EP4581200A1

EP4581200A1 - A yarn piecing system and method for piecing auxiliary yarn at a spinning station of a ring spinning machine requiring repairment

Info

Publication number: EP4581200A1
Application number: EP22798288.1A
Authority: EP
Inventors: Gabriele POLLONO
Original assignee: Pinter Caipo SAU
Current assignee: Pinter Caipo SAU
Priority date: 2022-08-29
Filing date: 2022-09-30
Publication date: 2025-07-09
Also published as: JP2025529191A; CN119790194A; WO2024046587A1

Abstract

A yarn piecing system for threading and piecing auxiliary yarn (1), comprising a yarn handling tool (6) attached to a computer-controlled mechanical arm or robotic arm (7), a yarn nozzle (9) on the yarn outlet of the yarn handling tool (6), yarn holding means (16) arranged on the yarn handling tool (6) to be able to form a threading section of auxiliary yarn (1), and processing and control means configured to provide an activation signal to the drive means of the robotic arm (7) for the yarn handling tool (6) to carry out threading and piecing operations, wherein the system further comprises a yarn feeding device (10) arranged and configured for feeding a length ("L0", "LI") of auxiliary yarn (1) to a yarn conveying path outside the yarn handling tool during operation of the yarn handling tool by the robotic arm.

Description

A YARN PIECING SYSTEM AND METHOD FOR PIECING AUXILIARY YARN AT A SPINNING STATION OF A RING SPINNING MACHINE REQUIRING REPAIRMENT

The present invention generally relates to a yarn piecing system for piecing auxiliary yarn when a yarn break occurs at a spinning station of a ring spinning machine. It also relates to a method for automatic piecing of auxiliary yarn at a spinning station.

Background of the invention

Known yarn piecing systems carry out an automatic piecing of a broken end of yarn. When a yarn break occurs on a ring spinning machine, the broken end of yarn is wound on a bobbin after breakage. In those systems, an automatic yarn handling device is used for detecting the broken end of the yarn by means of a suction tube connected to a vacuum source. The suction tube is mounted on an automatic service station arranged displaceable along a row of spinning stations with an option of stopping at a selected spinning station requiring a service operation.

In the above-mentioned known yarn piecing systems, to resume spinning after a yarn breakage, the yarn end is sucked into the vacuum tube by which the yarn end is positioned with respect to the bobbin and, subsequently, a threading operation is carried out by creating a threading section of the yarn end. The threading section is positioned at the flange of the ring and a traveller on the ring of the spinning machine is set into motion by compressed air so that it is put onto the threading section of the yarn end and the yarn end is threaded into the traveller. Once threaded, the yarn end is positioned by means of the same suction tube for piecing to roving issuing from roving delivery rollers.

Yarn piecing systems dealing with broken ends of yarn have the drawback that broken ends are difficult to detect when breakage of yarn takes place after a bobbin change (doffing) where the spindle tube is still empty of yarn. Likewise, broken ends are difficult to detect if they keep wrapped on a section of the spindle tube located below the ring rail of the spinning machine. This situation arises when two spinning stations require simultaneous service operation and the automatic service station takes more time than required to assist the second spinning station so that a significant section of spindle tube of the second spinning station is empty of yarn above the ring rail.

To solve the shortcomings of yarn piecing systems dealing with broken ends of yarn, known piecing systems have been developed to improve the process of piecing by supplying a free end of auxiliary yarn to a spindle tube of a revolving spindle onto which the free end is to be wrapped. Those known yarn piecing systems may dispense with the step of detecting the broken end of yarn. JP03199436A discloses one said known yarn piecing systems having an automatic service station which can be positioned at a spinning station for supplying a free end of auxiliary yarn from an auxiliary yarn source to a revolving spindle having a spindle tube providing a winding surface onto which the free end is to be wrapped. The free end of auxiliary yarn is supplied from a yarn feeding nozzle propelling the free end of auxiliary yarn together with air to the spindle tube of the revolving spindle. The system is also provided with a finger element to fasten auxiliary yarn on outside the yarn feeding nozzle to form a threading section once the free end of auxiliary yarn is wrapped onto the spindle tube. To this end, automatic handling means are provided to handle both the yarn feeding nozzle and the finger element to carry out the threading operation. Once threaded, the yarn end of the auxiliary yarn is positioned by means of another finger element for piecing it to roving issuing from front rollers of the drafting assembly.

The yarn piecing system disclosed by JP03199436A has several shortcomings. One of said shortcomings is that of failure of the wrapping operation of the free end of auxiliary yarn to the spindle tube caused by poor adherence of the free end of auxiliary yarn to the surface of the spindle tube, in particular, when the spindle tube is empty of yarn after doffing. Another shortcoming is that the threading operation takes place while the spindle tube keeps rotating for an appropriate tension acts on the auxiliary yarn on outside the yarn feeding nozzle and prevents the threading section from sagging. Nevertheless, in practice it is found that by rotation of the spindle tube the threading operation is even more difficult and complex to be carried out since threading demands high preciseness when positioning the yarn.

It is, therefore, necessary to provide an alternative to the state of the art which covers the gaps found therein, by the provision of a yarn piecing system and method for piecing auxiliary yarn, which overcomes the above mentioned shortcomings, and hence provides a system having fast and reliable threading and piecing operations as well as improved reliability on the wrapping operation of the free end of auxiliary yarn, even with empty spindle tubes.

Description of the invention

To that end, the present invention relates, in a first aspect, to a yarn piecing system for piecing auxiliary yarn at a spinning station of a ring spinning machine requiring repairment, comprising; a yarn handling tool attached to a computer-controlled mechanical arm or robotic arm, drive means for the robotic arm, a yarn conveying path inside the yarn handling tool for conveying auxiliary yarn from a yarn inlet to a yarn outlet, a yarn nozzle on the yarn outlet of the yarn handling tool,

- yarn holding means arranged on the yarn handling tool to be able to form a threading section of auxiliary yarn on outside the yarn nozzle, and processing and control means configured to provide an activation signal to the drive means of the robotic arm for the yarn handling tool to carry out both threading and piecing operations once the free end of auxiliary yarn is wrapped onto the spindle and rotation of the spindle is stopped, wherein the system further comprises; a yarn conveying path outside the yarn handling tool for conveying auxiliary yarn from an auxiliary yarn source to the yarn inlet of the yarn handling tool, and a yarn feeding device arranged and configured for feeding a length of auxiliary yarn to the yarn conveying path outside the yarn handling tool during operation of the yarn handling tool by the robotic arm.

Thanks to the claimed features, the present invention provides a yarn piecing system wherein both threading and piecing operations are handled by means of a yarn handling tool attached to a robotic arm of an automatic service station, and wherein a yarn feeding device is arranged and configured for feeding a length of auxiliary yarn to the path outside the yarn handling tool during operation of the yarn handling tool by the robotic arm.

It is found that the auxiliary yarn outside the yarn handling tool loosens, twists, and rolls up on itself during operation causing curls of yarn that alter and interfere threading and piecing.

In the claimed system, the yarn feeding device feeds a length of auxiliary yarn to the path outside the yarn handling tool that serves as a yarn buffer and helps to improve the handling of the auxiliary yarn on outside the yarn handling tool by preventing curls and twists from forming while the robotic arm, or computer controlled mechanical arm, moves to carry out threading and piecing.

According to a second aspect, the present invention relates to a method of piecing auxiliary yarn at a spinning station of a ring spinning machine requiring repairment, comprising the steps of; a) feeding a first length of auxiliary yarn to a yarn conveying path outside a yarn handling tool driven by a robotic arm, b) approaching the yarn handling tool to a revolving spindle tube of a revolving spindle requiring repairment, c) propelling the first length of auxiliary yarn to a yarn outlet of the yarn handling tool for a free end of the auxiliary yarn to be wrapped onto the revolving spindle tube, d) after the free end of auxiliary yarn is wrapped onto the revolving spindle, stopping rotation of the revolving spindle, e) after step d), feeding a second length of auxiliary yarn to the yarn conveying path outside the yarn handling tool and increasing or reducing said second length of auxiliary yarn while the robotic arm moves the yarn handling tool to carry out threading and piecing.

In contrast to the known piecing methods, in the claimed method a first length of auxiliary yarn is fed to the yarn path outside to the yarn handling tool to precisely prepare a length of yarn for being propelled and being wrapped onto the spindle tube.

Once the free end of the auxiliary yarn is wrapped, rotation of the revolving spindle is stopped, and a second length of auxiliary yarn is fed along the yarn path outside the yarn handling tool. Movement back and forward of the yarn handling tool by the robotic arm causes this second length of auxiliary yarn to increase or reduce to allow the threading and piecing operations to take place without sagging of the yarn. In this manner, reliability and preciseness of both threading and piecing operations is significantly improved.

For one embodiment, the yarn feeding device of the claimed system is preferably configured for feeding the length of auxiliary yarn under tension, and steps a) and e) of the claimed method take place preferably by respectively feeding the first length of auxiliary yarn under tension and the second length of auxiliary yarn under tension.

Advantageously, the yarn piecing system comprises a yarn buffer mechanism to form a yarn buffer of auxiliary yarn along the yarn conveying path outside the yarn handling tool in between the yarn handling tool and the auxiliary yarn source, and a control unit for the yarn buffer mechanism.

It has been found the yarn buffer helps to improve the handling of the auxiliary yarn on outside the yarn handling tool by preventing curls and twists from being formed while the robotic arm or computer controlled mechanical arm moves to carry out threading and piecing.

For a preferred embodiment, the yarn buffer mechanism is configured to form a yarn buffer of tensioned auxiliary yarn to counteract the curling and twisting of the length of auxiliary yarn more efficiently along the path outside the yarn handling tool.

For the preferred embodiment including the yarn buffer mechanism, a method of piecing auxiliary yarn is claimed wherein; step a) comprises forming a yarn buffer including the first length of auxiliary yarn along a yarn conveying path outside the yarn handling tool, step c) comprises propelling the first length of auxiliary yarn of the yarn buffer to a yarn nozzle of the yarn handling tool for the free end of auxiliary yarn of the yarn buffer to be wrapped onto the revolving spindle tube, and step e) comprises; i. forming a yarn buffer including the second length of auxiliary yarn and ii. holding under elastic tension the second length of auxiliary yarn of the yarn buffer while said second length of auxiliary yarn increases or reduces as the robotic arm moves the yarn handling tool to carry out a threading operation and a piecing operation.

Advantageously, the yarn processing and control means are configured to supply a signal to the control unit of the yarn buffer mechanism for the yarn buffer mechanism to form the yarn buffer including a predetermined length of auxiliary yarn at a launching step of the piecing cycle.

Thanks to these features, it is possible to feed a predetermined length of auxiliary yarn along the path outside the yarn handling tool in between the auxiliary yarn source and the yarn inlet of the yarn handling tool. This predetermined length of auxiliary yarn is set for being propelled to the revolving spindle at a launching step of the piecing cycle. Depending on the type of yarn the length of yarn for propelling may be different. Since the length of auxiliary yarn to be propelled is prepared by the yarn buffer mechanism, handling of the auxiliary yarn takes place more efficiently without risk of sagging or curling.

For one embodiment, the yarn buffer mechanism comprises a yarn holding member configured and arranged to hold the auxiliary yarn of the yarn buffer under elastic tension while the auxiliary yarn of the yarn buffer increases or reduces as the robotic arm moves the yarn handling tool.

The yarn holding member may be configured to hold the auxiliary yarn under elastic tension at constant torque for the elimination of curls and tangles of the yarn. During operation of the yarn handling tool by the robotic arm, the auxiliary yarn of the yarn buffer increases or reduces to keep the auxiliary yarn along the path outside the yarn handling tool under tension at a constant value.

For one embodiment, the control unit for the yarn buffer mechanism comprises a stepper motor operationally connected to the yarn holding member to keep the yarn holding member to an active elastic working position while the auxiliary yarn of the yarn buffer increases or reduces as the robotic arm moves the yarn handling tool.

The stepper motor is operationally connected to the yarn holding member so that it is made to work at a lower current mode to keep the yarn holding member to the active elastic working position. In the active elastic working position the stepper motor allows the yarn holding member to acquire a retracted position when pulled by the movement of the robotic arm resulting on the length of accumulated yarn of the yarn buffer to be reduce, and to recover an initial extended position when the robotic arm moves closer to the yarn buffer mechanism resulting on the length of accumulated yarn of the yarn buffer to be increased.

Advantageously, the same stepper motor is made to work at a high current mode for the yarn holding member to acquire a predetermined extended position to form a yarn buffer including a predetermined length of auxiliary yarn at a launching step of the piecing cycle. This predetermined length of auxiliary yarn of the yarn buffer comes from an auxiliary yarn source. The stepper motor may be operated to move the yarn holding member to different fixed positions to be able to take the necessary length of auxiliary yarn from the auxiliary yarn source.

For one embodiment, the yarn holding member comprises a yarn handling rod operationally connected to the control unit of the yarn buffer mechanism and said yarn handling rod is arranged to pivot an angle of rotation upon the control unit receives the signal from the processing and control means to form the yarn buffer.

The yarn handling rod may be a flexible rod and, advantageously, the yarn handling rod is arranged to accumulate potential energy in an active elastic working position to keep the auxiliary yarn of the yarn buffer tensioned at a predetermined value while the auxiliary yarn of the yarn buffer increases or reduces as the robotic arm moves the yarn handling tool to carry out threading and piecing.

Preferably, the yarn piecing system comprises yarn propelling means arranged along the yarn conveying path inside the yarn handling tool, and the processing and control means are configured to supply an activation signal to the yarn propelling means for said yarn propelling means to be able to propel the length of auxiliary yarn of the yarn buffer to the yarn nozzle for the free end of the auxiliary yarn of the yarn buffer to be wrapped onto a revolving spindle at a yarn launching step of the piecing cycle.

The yarn propelling means pull the length of auxiliary yarn of the yarn buffer and push it to the yarn nozzle for the free end of auxiliary yarn to be wrapped onto the revolving spindle tube.

According to one embodiment of the system, the yarn propelling means comprise a Venturi tube and air injector assembly arranged to suction air into the yarn inlet of the yarn handling tool upon receiving an activation signal from the processing and control means. This Venturi tube and air injector assembly is mounted on the handling tool, and preferably, it is arranged so that the Venturi tube is substantially aligned with the yarn nozzle. When activated the yarn propelling means pick up yarn from the yarn inlet and pushes it towards the yarn outlet or yarn nozzle of the yarn handling tool. The yarn propelling means may include or not a Venturi tube. For example, they may not include a Venturi tube and be configured by way of a mechanical air-based device. For a preferred embodiment, the piecing system comprises liquid supply means, preferably, liquid spray means, arranged to be able to wet a yarn contact area of the revolving spindle tube intended to be contacted by the free end of auxiliary yarn at a yarn launching step of the piecing cycle.

According to this preferred embodiment, the processing and control means are configured to supply an activation signal to the liquid supply means to supply liquid spray onto the yarn contact area of the revolving spindle tube while the free end of auxiliary yarn is propelled to the said yarn contact area of the revolving spindle tube.

It has been found that the rate of success for the free end of auxiliary yarn to be wrapped onto the revolving spindle is significantly increased when a liquid spray is supplied towards the spindle tube to wet the yarn contact area intended to be contacted by the free end of auxiliary yarn at the launching step of the piecing cycle. Besides, the catching time is significantly reduced to an average time of three seconds versus an average time of nineteenth seconds when dispensing with the use of liquid spray.

For one embodiment, the yarn handling tool is articulately attached to the robotic arm by means of an articulated joint, said articulated joint being configured to allow a tilting base of the yarn handling tool to pivot to an angled position to absorb heigh discrepancies of the working position of a movable support rail of the ring spinning machine.

It is well-known that the movable support rail, which support the revolving spindles, moves up and down during spinning. Thus, the robotic arm must track the movement of the movable support rail to carry out threading and piecing operations. To this end, a positioning sensor (e.g., a laser sensor) is fixed in one end of the ring spinning machine to be able to supply height position data to the controller of the robotic arm at any time of the piecing cycle. Nevertheless, the length of the movable support rail does not guarantee that the height position data provided by the positioning sensor are correct at the spinning station requiring repairment. If the height position data are not correct the robotic arm cannot correctly position the yarn handling tool to carry out threading.

The claimed articulated joint allows the yarn handling tool to absorb heigh discrepancies and to acquire an optimal work angle to carry out threading.

Preferably, the articulated joint comprises an elastic connection arranged to allow the tilting base of the yarn handling tool to pivot to an angled position upon contacting the movable support rail, and to recover an initial resting position when ceasing contact with the movable support rail.

Advantageously, for the embodiment with the articulated joint, the piecing system comprises a tool angle sensor assembly connected operatively to a controller unit of the robotic arm to set the yarn handling tool at an optimal working angled position upon contacting the movable support rail.

Preferably, the tool angle sensor assembly comprises a at least two proximity sensors for detecting presence of the tilting base of the yarn handling tool, and the controller unit is configured to check the status of the at least two proximity sensors and to supply a setting up signal to the processing and control means for said processing and control means order synchronization of movement of the robotic arm with movement of the movable support rail according to a calculated height offset value.

These proximity sensors may be arranged on the rear part of a frame structure of the yarn handling tool to set up the optimal working angled position of the yarn handling tool upon contacting the movable support rail. The controller unit of the robotic arm sends the signal to the processing and control means of the system to be able to carry out synchronization of the movement of the robotic arm with up and down movement of the movable support rail.

Advantageously, the processing and control means are configured;

- to obtain an actual working height position of the movable support rail at the spinning station requiring repairment based on the angled position of the yarn handling tool provided by the controller unit of the robotic arm,

- to calculate a height offset value to be applied to height position data of the movable support rail provided by a positioning sensor (e.g., a laser sensor fixed in one end of the ring spinning machine), and

- to send a signal to the controller unit of the robotic arm to synchronize movement of the robotic arm with movement of the movable support rail based on the calculated height offset value.

When synchronization is done, the robotic arm starts following the movable support rail so that all the movements needed to carry out threading into a ring traveller will be merged with the movements of the tracking of the movable support rail.

For a preferred embodiment, the yarn piecing system comprises yarn cutter means arranged on the yarn conveying path inside the yarn handling tool for cutting auxiliary yarn inside the yarn path of the yarn handling tool upon receiving a cutting signal from the processing and control means.

The yarn cutter means may be configured by a small blade or cutter integrated on the yarn handling tool to be able to cut the auxiliary yarn in the yarn path inside the yarn handling tool so that the free end of the auxiliary yarn does not protrude outside the yarn nozzle of the yarn handling tool once cut. The blade or cutter may be driven by an electromagnet or air actuator.

Preferably, the yarn piecing system comprises yarn retaining means arranged on the same yarn conveying path inside the yarn handling tool to retain in place the auxiliary yarn on the path inside the yarn handling tool, for example, when the auxiliary yarn has been cut.

For one embodiment, the piecing system is prepared to carry out a yarn self-threaded procedure in case of yarn loss along the yarn conveying path inside the yarn handling tool. Yarn loss is detected by means of sensor means configured to detect presence and/or movement of the yarn inside the yarn handling tool. The sensor means are connected operatively to the processing and control means to inform the system about the state of the auxiliary yarn inside the tool. To be able to carry out the yarn self-threaded procedure, the yarn piecing systems comprises the yarn feeding device including; a yarn outlet of the yarn buffer mechanism,

- yarn retaining means arranged to retain in place a free end of auxiliary yarn on outside the yarn outlet of the yarn buffer mechanism, and air blowing means arranged to inject air into the yarn outlet of the yarn buffer mechanism.

The processing and control means are configured to carry out the automatic selfthread operation including the steps of; i. supplying a signal to the drive means of the robotic arm for the robotic arm to position the yarn inlet of the yarn handling tool in correspondence with the yarn outlet of the yarn buffer mechanism, ii. supplying an activation signal to the air blowing means of the yarn feeding device to blow the free end of auxiliary yarn on outside the yarn outlet of the yarn buffer mechanism while retaining in place the auxiliary yarn of the yarn buffer on outside the yarn outlet, and iii. supplying an activation signal to the yarn propelling means of the yarn handling tool for said free end of auxiliary yarn of the yarn buffer to be suctioned along the yarn conveying path inside the yarn handling tool.

Advantageously, the yarn feeding device further comprises a yarn cutter connected operatively to the yarn outlet of the yarn buffer mechanism to be able to cut excess of yarn outside the yarn outlet in case of yarn loss and, preferably, the air blowing means comprise a Venturi tube and air injector assembly arranged to blow or inject air into the yarn outlet of the yarn buffer mechanism upon receiving a signal from the processing a control means.

Again advantageously, the yarn conveying path inside the yarn handling tool is configured airtight to keep an optimal airflow generated by the yarn propelling means of the yarn handling tool. It has been found that in case of yarn loss, this helps the free end of auxiliary yarn on outside the yarn buffer mechanism to be efficiently suctioned inside the yarn handling tool and thrown to the yarn nozzle of the tool. For one embodiment, the piecing system comprises image capture means arranged preferably on the yarn handling tool, wherein the image capture means are operatively connected to an artificial vision system configured to check whether there are impediments to do the piecing before the piecing cycle starts (e.g., yarn pieces knotted on the pig-rail). For one embodiment, the image capture means (e.g., a camera) are arranged on the yarn handling tool.

In contrast to known piecing systems dealing with broken ends of yarn, the claimed piecing system is suitable for using either with empty spindle tubes (after doffing) and with spindle tubes holding spun fibres (yarn package), since a free end of auxiliary yarn is always supplied to the spindle tube for wrapping. Besides, the claimed method and system have a hight reliability because at the launching phase a predetermined length of auxiliary yarn of the yarn buffer (i.e. , a controlled yarn length) is propelled to the yarn nozzle for the free end of the auxiliary yarn of the yarn buffer to be wrapped onto a revolving spindle tube. Moreover, the yarn is preferably propelled towards a yarn contact area of the spindle tube that has been previously or simultaneously wetted with liquid, for example, with liquid spray or pulverized water. This yarn contact area may be an area of the spindle tube empty of yarn or an area of the spindle tube with existent yarn.

As previously stated, it has been found that the rate of success for the free end of auxiliary yarn to be wrapped onto the revolving spindle is significantly increased by wetting the yarn contact area intended to be contacted by the free end of auxiliary yarn at the launching step of the piecing cycle. Besides, the catching time is significantly reduced to an average time of three seconds versus an average time of nineteenth seconds when dispensing with the use of liquid spray. The reduction of time spent to grab the free end of yarn is particularly significative when the contact area of the spindle tube is empty of yarn (after doffing).

Below is a table providing results of success rate and average catching time for grabbing auxiliary yarn obtained from a yarn launching test with and without spraying water onto the yarn contact are of the revolving spindle tube.

Although the supply of liquid to wet the yarn contact area of the revolving spindle has been disclosed in combination with a yarn piecing system including a yarn handling tool and a yarn feeding device for feeding a length of auxiliary yarn to the yarn conveying path outside the yarn handling tool, the applicant reserves the right to claim as an separated invention a yarn piecing system for threading and piecing a free end of auxiliary yarn at a spinning station of a ring spinning machine requiring repairment, comprising;

- yarn supplying means for supplying a free end of auxiliary yarn to a spindle tube of a revolving spindle onto which said free end is to be wrapped, said yarn supplying means including a yarn nozzle for feeding a free end of said auxiliary yarn to the spindle tube of said revolving spindle,

- yarn holding means for holding auxiliary yarn on outside the yarn feeding nozzle to form a threading section of auxiliary yarn once the free end of the auxiliary yarn is wrapped onto the spindle tube, and automatic handling means for handling the yarn supplying means and the yarn holding means, wherein the system further comprises; liquid supply means arranged to be able to wet a yarn contact area of the revolving spindle intended to be contacted by the free end of auxiliary yarn at a yarn launching step of the piecing cycle, and processing and control means configured to supply an activation signal to the liquid supply means to supply liquid spray onto the yarn contact area of the revolving spindle tube before and/or while the free end of auxiliary yarn is propelled to the said yarn contact area of the revolving spindle.

Preferably, the liquid supply means comprise liquid spray means. The liquid may be pulverised or applied in any other way on condition that the yarn contact area of the revolving spindle is wet. The yarn contact area may be an area of the revolving spindle tube with yarn or an area of the revolving spindle empty of yarn.

For one embodiment, the automatic handling means include a yarn handling tool attached to a computer-controlled mechanical arm or robotic arm and both the liquid supply means and the yarn nozzle are arranged on the yarn handling tool.

Advantageously, the yarn holding means are arranged on the yarn handling tool, and the processing and control means are configured to provide an activation signal to the drive means of the robotic arm for the yarn handling tool to carry out both threading and piecing operations once the free end of auxiliary yarn is wrapped onto the spindle and rotation of the spindle is stopped.

For one embodiment, the yarn piecing system comprises a yarn buffer mechanism to form a yarn buffer of auxiliary yarn along a yarn conveying path outside the yarn handling tool in between the yarn handling tool and an auxiliary yarn source, and a control unit for the yarn buffer mechanism.

Advantageously, according to the embodiment of the system with the yarn buffer mechanism, the processing and control means are configured to supply an activation signal to the yarn propelling means for said yarn propelling means to be able to propel the length of auxiliary yarn of the yarn buffer to the yarn nozzle for the free end of the auxiliary yarn of the yarn buffer to be wrapped onto a revolving spindle at a yarn launching step of the piecing cycle.

In the present invention;

By robotic arm shall be understood a robotic arm or a computer-controlled mechanical arm, preferably, a computer-controlled arm with at least six degrees of freedom of movement.

By threading operation shall be understood the operation of creating or forming a threading section of auxiliary yarn on outside the yarn nozzle of the yarn handling tool, and handling the threading section at the flange of the ring of the ring spinning machine for said threading section is threaded into the ring traveller of the ring spinning machine.

By piecing operation shall be understood the operation of positioning the yarn handling tool for piecing threaded auxiliary yarn on the roving issuing the front drafting rollers of the drafting assembly of the ring spinning machine.

A piecing cycle of the claimed method and system shall be understood to include both threading and piecing operations.

Brief description of the drawings

The previous and other advantages and features will be more fully understood from the following detailed description of embodiments, with reference to the attached drawings, which must be considered in an illustrative and non-limiting manner, in which summarizing;

In detail:

Figure 1 shows a perspective view of an embodiment of a yarn handling tool attached to a robotic arm (for the sake of clarity only a part of the robotic arm is represented). This figure also shows a camera attached to the robotic arm for capturing images to check whether there are impediments to do the piecing, and a liquid spray nozzle attached to the frame structure of the yarn handling tool and aligned vertically with a yarn nozzle arranged at the yarn outlet of the yarn handling tool for feeding the auxiliary yarn to a revolving spindle tube.

Figure 2 shows a schematic perspective rear view of the yarn handling tool attached to the robotic arm and approaching to an empty revolving spindle tube. It also shows a yarn feeding device interposed in between the yarn handling tool and an auxiliary yarn source (not shown), and a movable support rail where a plurality of revolving spindle tubes is mounted each revolving spindle tube belonging to a different spinning station of the ring spinning machine. This figure 2 shows an embodiment of the yarn feeding device including a yarn buffer mechanism forming a yarn buffer of auxiliary yarn along the yarn conveying path outside the yarn handling tool. The yarn buffer includes a first length “L0” of auxiliary yarn which has been fed to the yarn path outside the yarn handling tool for being propelled towards a revolving spindle tube at a launching step of the piecing cycle.

Figure 3 shows a schematic perspective view of the yarn handling tool attached to the robotic arm with the yarn nozzle propelling the first length “L0” of auxiliary yarn of the yarn buffer and the liquid spray nozzle supplying liquid spray to wet the yarn contact area of the empty revolving spindle while the free end of auxiliary yarn is propelled to the said yarn contact area.

Figure 4 shows a schematic perspective analogue to that of figure 2 wherein the yarn buffer mechanism is forming a yarn buffer of auxiliary yarn including a second length “L1” of auxiliary yarn which has been fed to the yarn path outside the yarn handling tool after the free end of the auxiliary yarn is wrapped and rotation of the spindle tube stopped. Movement back and forward of the yarn handling tool by the robotic arm will cause this second length “L1” of auxiliary yarn to increase or reduce to allow the threading operation to take place without sagging of the yarn and by preventing curls and twists from forming along the yarn path outside the yarn handling tool.

Figure 5 is a perspective view of the yarn handling tool showing a threading section of auxiliary yarn formed on outside the yarn nozzle by means of a holding element (e.g., a grip) arranged on the yarn handling tool. Precise motion of the yarn handling tool is required for the yarn handling tool causes the holding element to hold or grasp the auxiliary yarn on outside the yarn nozzle to form the threading section. Once formed, the threading section must be threaded by a ring traveller mounted on a ring supported on the movable support rail of the corresponding spindle tube.

Figure 6 is a side view of the yarn handling tool of figure 1 attached to the robotic arm by means of an articulated joint configured to allow a tilting base of the yarn handling tool to pivot to an angled position to absorb heigh discrepancies of the working position of the movable support rail and to acquire an optimal work angle before carrying out threading.

Figures 7a and 7b show a rear perspective view of the yarn handling tool approaching the movable support rail to touch it just enough to set by means of a tool angle sensor assembly the yarn handling tool at an optimal working position upon contacting the movable support rail. A controller unit of the robotic arm (not shown) is configured to check the status of the two proximity sensors arranged for detecting presence of the tilting base of the yarn handling tool. The controller unit of the robotic arm supply a setting up signal to the processing and control means (not shown) of the system for said processing and control means order synchronization of movement of the robotic arm with movement of the movable support rail according to a calculated height offset value applied to height position data provided by a positioning sensor (e.g., a laser sensor measuring heigh position of the movable support rail at one end of the ring spinning machine).

Figure 8 shows a perspective view of the yarn handling tool attached to the robotic arm while the threading section of auxiliary yarn is about to be threaded by the ring traveller. An air conduct attached to the surface of the yarn handling tool propels air to move the ring traveller on the flange of the ring to facilitate threading.

Figure 9 shows a schematic bottom view of the yarn handling tool showing the interior components arranged on the yarn conveying path inside the yarn handling tool for conveying the length of auxiliary yarn from the yarn inlet to the yarn outlet which is configured by way of the yarn nozzle. Along this path there are arranged yarn propelling means, yarn cutter means, yarn retaining means and sensor means for detecting presence and/or movement of the length of auxiliary yarn.

Figure 10 shows a schematic exploded view of the yarn handling tool from a bottom view.

Figure 11 is a schematic bottom view of the yarn handling tool of figure 9 showing a detailed partial section of the portion of the yarn path inside the yarn handling tool wherein the yarn cutter is arranged for cutting the auxiliary yarn. This figure shows the piece of length of auxiliary yarn blown out of the yarn nozzle once it has been cut by the yarn cutter inside the yarn handling tool.

Description of preferred embodiments

Following is a description of the claimed invention with reference to drawings of figures 1 to 11 representing an exemplary embodiment of the system and method applicable to a ring spinning machine, which comprises a row of spinning stations arranged next to each other.

The claimed yarn piecing system and method is provided for supplying automatic service to any spinning station of the ring spinning machine requiring repairment after yarn breakage. As stated, the claimed piecing system and method supply a free end of auxiliary yarn 1 to a revolving spindle having a revolving spindle tube 2 providing a winding surface onto which the free end is to be wrapped for the system subsequently carries out threading and piecing operations. The revolving spindles of the ring spinning machine are mounted aligned on a movable support rail 3 which moves up and down during spinning. At each spinning station, a ring 4 is attached to the movable support rail 3 and a ring traveller 5 is movable mounted on a flange of the ring 4. Each revolving spindle is arranged coaxially in a vertical position with respect the ring 4 and a respective spindle tube 2 is placed on the revolving spindle to support a package of yarn formed by spinning in a well-known manner, resulting in the formation of a cop. During spinning, the ring traveller 5 and the yarn threaded therein run round the spindle tube 2 on the flange of the ring 4 for the yarn is wound onto the surface of the spindle tube 2. Arranged above each revolving spindle tube 2 is a balloon constriction ring (not shown), a yarn guide (not shown) and a drafting assembly (not shown) including rear, middle and front drafting rollers from which drafted roving issues.

The present invention provides a yarn piecing system and method wherein both threading and piecing operations are handled by means of a yarn handling tool 6 attached to a robotic arm 7 of an automatic service station including a carriage arrangement (not shown) on which the robotic arm 7 is mounted. The carriage is displaceable along the row of spinning stations of the ring spinning machine.

For the illustrated embodiment, a camera 29 is arranged on the robotic arm 7 operatively connected to an artificial vision system configured to check whether there are impediments to do the piecing. If the captured images found that something will compromise the piecing, the processing and control means of the system request the intervention of an operator to restore the normal working conditions for the yarn piecing system to be able to give automatic service.

Arranged inside the yarn handling tool 6 there is a yarn conveying path for conveying auxiliary yarn 1 from a yarn inlet 8 to a yarn outlet of the yarn handling tool 6 configured by way of a yarn nozzle 9. Outside the yarn handling tool 6 there is a yarn conveying path for conveying auxiliary yarn 1 from an auxiliary yarn source (not shown) to the yarn inlet 8 of the yarn handling tool 6. A yarn feeding device 10 is mounted on the same carriage arrangement and is configured for feeding a length of auxiliary yarn 1 to the yarn conveying path outside the yarn handling tool 6. This length of auxiliary yarn 1 outside the yarn handling tool 6 has been found to serve as a yarn buffer which helps to improve handling of the auxiliary yarn 1 on outside the yarn handling tool 6.

According to a preferred embodiment of the system and method, the yarn feeding device 10 includes a yarn buffer mechanism 11 forming a yarn buffer of auxiliary yarn 1 along the yarn conveying path outside the yarn handling tool 6. The yarn buffer includes a first length “L0” of auxiliary yarn 1 which has been fed to the yarn path outside the yarn handling tool 6 for being propelled towards a revolving spindle tube 2 at a launching step of the piecing cycle (see, figure 2).

In the disclosed embodiment, the yarn buffer mechanism 11 includes a yarn holding member 12 configured and arranged to hold the auxiliary yarn 1 of the yarn buffer under elastic tension. This yarn holding member 12 includes a yarn holding rod operatively connected to a control unit (not shown) of the yarn buffer mechanism 11 to pivot an angle of rotation upon the control unit receives a signal coming from processing and control means of the system to form the yarn buffer.

For the illustrated embodiment of figures 2 and 4, the control unit of the yarn buffer mechanism 11 includes a stepper motor 13 operatively connected to the yarn holding rod for pivoting the yarn holding rod at different fixed positions to be able to take the necessary length of auxiliary yarn 1 from the auxiliary yarn source.

At the launching step of the piecing cycle, the yarn processing and control means of the system supply a signal to the control unit of the yarn buffer mechanism 11 to form the yarn buffer with a predetermined length (e.g., the first length “L0”) of auxiliary yarn coming from the auxiliary yarn source. The length of auxiliary yarn 1 of the yarn buffer necessary for launching may be different depending among others on the type of yarn to be pieced.

To propel the predetermined length of auxiliary yarn 1 of the yarn buffer towards the revolving spindle tube 2 the yarn piecing system includes yarn propelling means arranged on the yarn path inside the yarn handling tool 6. For the illustrated embodiment, the yarn propelling means comprise a Venturi tube and air injector assembly 14 arranged to suction air into the yarn inlet 8 of the yarn handling tool 6 upon receiving a signal from the processing and control means to propel the length of auxiliary yarn 1 of the yarn buffer through the yarn nozzle 9.

Advantageously, the yarn piecing system comprises liquid supply means arranged to be able to wet a yarn contact area of the revolving spindle tube 2 intended to be contacted by the free end of auxiliary yarn 1 at the launching step of the piecing cycle. The processing and control means of the system are configured to supply an activation signal to the liquid supply means to supply liquid spray (e.g., pulverized water) onto the yarn contact area of the revolving spindle tube 2 while the free end of auxiliary yarn 1 is propelled to the said yarn contact area.

The liquid supply means comprises a liquid spray nozzle 15 associated with a container of liquid (not shown) and with two solenoid valves (not shown) to control passage of liquid and air for pulverizing a small amount of liquid in a jet of air. In the illustrated embodiment, the liquid spray nozzle 15 is arranged on the yarn handling tool 6 aligned vertically with the yarn nozzle 9 of the yarn handling tool 6 but rather may not be necessarily arranged on the yarn handling tool 6. Figure 3 shows a schematic perspective view of the yarn handling tool 6 attached to the robotic arm 7 with the yarn nozzle 9 propelling the first length “L0” of auxiliary yarn 1 of the yarn buffer and the liquid spray nozzle 15 supplying liquid spray to wet the yarn contact area of the empty revolving spindle tube 2 while the free end of auxiliary yarn 1 is propelled to the said yarn contact area.

As previously stated, it has been found that the rate of success for the free end of auxiliary yarn to be wrapped onto the revolving spindle tube 2 is significantly increased (98% vs 46%) when a liquid spray is supplied towards the spindle tube 2 to wet the yarn contact area. Besides, the catching time is significantly reduced to an average time for grabbing of three seconds versus an average time of nineteenth seconds when dispensing with the use of liquid spray. Wetting eliminates electrostatic effect and increases adhesion of the auxiliary yarn 1 onto the surface of the revolving spindle tube 2.

After the free end of the auxiliary yarn is successfully wrapped onto the surface of the revolving spindle tube 2, rotation of the spindle is stopped and the stepper motor 13 of yarn buffer mechanism 11 actuates the yarn holding member 12 to an initial retracted position. Subsequently, the yarn feeding device 10 supplies a second length “L1” of auxiliary yarn 1 to the yarn path outside the yarn handling tool 6. Since the end of auxiliary yarn 1 is fixed to the revolving spindle tube 2, the length “L1” of auxiliary yarn 1 is supplied from the auxiliary yarn source upon the yarn holding rod is made to pivot to a new predetermined angled position actuated by the stepper motor 13 (see, figure 4).

Movement of the yarn handling tool 6 by the robotic arm 7 to carry out threading causes this second length “L1 ” of auxiliary yarn 1 to increase or reduce to allow this operation to take place without sagging and with the auxiliary yarn 1 outside the yarn handling tool 6 being kept under tension and free of curls. To this end, the stepper motor 13 is made to work at a lower current mode to keep the yarn holding rod to an elastic active working position while the auxiliary yarn 1 of the yarn buffer increases or reduces as the robotic arm 7 moves the yarn handling tool 6 back and forward. In the elastic active working position, the stepper motor 13 allows the yarn holding member 12 to acquire a partial retracted position when pulled by the movement of the robotic arm 7 resulting on the second length “L1” of auxiliary yarn 1 of the yarn buffer to be reduced. The yarn holding member 12 recovers an extended position when the robotic arm 7 moves closer to the yarn buffer mechanism 11 resulting on the second length “L1” of auxiliary yarn 1 of the yarn buffer to be increased. Yarn brakes 17, 18 are arranged along the path outside the yarn handling tool 6. An entrance yarn brake 17 controls the entrance of auxiliary yarn 1 to the yarn buffer from the yarn source and an output yarn brake 18 controls the output of auxiliary yarn 1 of the yarn buffer. Both brakes 17, 18 are operatively connected to the controller unit of the yarn buffer mechanism 11 . Figure 5 is a perspective view of the yarn handling tool showing a threading section of auxiliary yarn 1 formed on outside the yarn nozzle 9 by means of a holding element 16 (e.g., a grip) arranged on the yarn handling tool 6. This threading section must be threaded by the ring 5 traveller mounted on a ring 4 supported on the movable support rail 3 of the corresponding spindle tube 2.

Before carrying out threading the robotic arm 7 brings the yarn handling tool 6 closer to the movable support rail 3 making the yarn handling tool 6 to contact the movable support rail 3.

As previously stated, it is well-known that the movable support rail 3, which support the revolving spindles tubes 2, moves up and down during spinning. Thus, the robotic arm 7 must track the movement of the movable support rail 3 to carry out threading and piecing. To this end, a positioning sensor 19 (e.g., a laser sensor) is fixed in one end of the ring spinning machine to be able to supply height position data to the controller of the robotic arm 7 at any time of the piecing cycle. Nevertheless, the length of the movable support rail 3 does not guarantee that the height position data provided by the positioning sensor 19 are correct at the spinning station requiring repairment. If the height position data are not correct the robotic arm 7 cannot correctly position the yarn handling tool 6 to carry out threading.

For the illustrated embodiment of the claimed system, the yarn handling tool 6 is articulately attached to the robotic arm 7 by means of an elastic articulated joint 20 arranged to allow a tilting base 21 of the yarn handling tool 6 to pivot to an angled position upon contacting the movable support rail 3, and to recover an initial resting position when ceasing contact with the movable support rail 3. A spring 30 interposed between the tilting base 21 and the frame 25 helps the tilting base 21 to recover the initial resting position. The articulated joint 21 allows the yarn handling tool 6 to absorb heigh discrepancies when contacting the movable support rail 3 and to acquire an optimal work angle to carry out threading (see, figures 6, 7a and 7b).

Advantageously, the piecing system further comprises a tool angle sensor assembly 22 connected operatively to the controller unit of the robotic arm 7 to allow setting the yarn handling tool at the optimal working angled position upon contacting the movable support rail 3, and to supply a signal to the processing and control means of the system for said processing and control means;

- to obtain an actual working height position of the movable support rail 3 based on the angled position of the yarn handling tool 6 provided by the controller unit of the robotic arm 7,

- to calculate a height offset value to be applied to height position data of the movable support rail 3 provided by a positioning sensor 19 (e.g., a laser sensor fixed in one end of the ring spinning machine), and

- to send a signal to the controller unit of the robotic arm 7 to synchronize movement of the robotic arm 7 with up and down movement of the movable support rail 3 based on the calculated height offset value.

The tool angle sensor assembly 22 comprises at least two proximity sensors 23, 24 for detecting presence of the tilting base 21 of the yarn handling tool 6. Figure 10 shows these proximity sensors 23, 24 arranged on the rear part of a frame structure 25 of the yarn handling tool 6.

Figures 7a and 7b show a rear perspective view of the yarn handling tool 6 approaching the movable support rail 3 to touch it just enough to set by means of the tool angle sensor assembly 22 the yarn handling tool 6 at the optimal working position upon contacting the movable support rail 3. The controller unit (not shown) of the robotic arm 7 is configured to check the status of two proximity sensors 23, 24 arranged for detecting presence of the tilting base 20 of the yarn handling tool 6. The controller unit of the robotic arm 7 supply a setting up signal to the processing and control means (not shown) of the system for said processing and control means order synchronization of movement of the robotic arm 7 with movement of the movable support rail 3 according to the calculated height offset value applied to height position data provided by the positioning sensor 19 (e.g., the laser sensor measuring heigh position of the movable support rail 3 at one end of the ring spinning machine).

When synchronization is done, the robotic arm 7 starts following the movable support rail 3 so that all the movements needed to carry out threading into a ring 5 traveller will be merged with the movements of the tracking of the movable support rail 3. As stated, threading takes place without the spindle tube 2 is rotating to obtain maximum preciseness.

Figure 8 shows a perspective view of the yarn handling tool 6 attached to the robotic arm 7 when the threading section of auxiliary yarn 1 is about to be threaded by the ring 5 traveller. An air conduct 31 is attached to the surface of the yarn handling tool 6 to propel air to move the ring 5 traveller on the flange of the ring 4.

Once the ring 5 traveller is threaded, the robot arm 7 moves the yarn handling tool 6 upwards and passes the yarn through the balloon constriction ring (not shown), and a yarn guide (not shown). A spindle brake (not shown) is released and the yarn handling tool 6 is raised until it takes the auxiliary yarn 1 up to the front rollers of the drafting assembly to carry out piecing of the auxiliary yarn 1 on the roving issuing the front rollers. Then, a cutter 26 integrated on the yarn handling tool 6 cut the auxiliary yarn 1 in the path inside the yarn handling tool 6 so that the free end of the auxiliary yarn 1 does not protrude outside the yarn nozzle 9 once cut. Yarn retaining means 27 are arranged on the same yarn conveying path inside the yarn handling tool 6 to retain in place the auxiliary yarn 1 after being cut. At this point the piecing cycle is finished and the robot arm 7 returns the yarn handling tool 6 to its initial position and moves to the next spinning station requiring piecing.

Figures 9, 10 and 11 show different views of the components of the yarn handling tool 6.

Figure 9 is a schematic bottom view of the yarn handling tool 6 including the yarn conveying path inside the yarn handling tool 6 for conveying the length of auxiliary yarn 1 from the yarn inlet 8 to the yarn outlet which is configured by way of the yarn nozzle 9. Along this path there are arranged the Venturi tube and air injector assembly 14 to suction air into the yarn inlet 8 to propel the length of auxiliary yarn 1 of the yarn buffer, the yarn cutter 26 driven by an electromagnet, the yarn retaining means 27 to retain the auxiliary yarn 1 inside the yarn handling tool 6 once has been cut, and sensor means 28 for detecting presence and/or movement of the length of auxiliary yarn 1 . The sensor means 28 are mostly used for the processing and control means order stopping the piecing in case of losing the auxiliary yarn 1 inside the yarn handling tool or to start a self-threading procedure.

Figure 10 is another schematic bottom view of the interior components of the yarn handling tool 6 showing a detailed section of the portion of the yarn path inside the yarn handling tool with the yarn cutter 26 arranged for cutting the auxiliary yarn 1 .

Figure 11 shows a schematic exploded view of the yarn handling tool 6 showing among other components the tool angle sensor assembly 22 with the at least two proximity sensors 23, 24 arranged on the rear part of a frame structure 25 for detecting presence of the tilting base 21 of the yarn handling tool 6.

The claimed system has the advantage that allows carrying out an automatic yarn self-threading procedure in case of yarn loss along the yarn conveying path inside the yarn handling tool 6. To be able to carry out this procedure, the yarn feeding device 10 further comprises; a yarn outlet (not shown) of the yarn buffer mechanism 11 ,

- yarn retaining means (not shown) arranged on the yarn feeding device 10 to retain in place a free end of auxiliary yarn 1 on outside the yarn outlet of the yarn buffer mechanism 11 , air blowing means (not shown) arranged to inject air into the yarn outlet of the yarn buffer mechanism 11 , and a yarn cutter (not shown) connected operatively to the yarn outlet of the yarn buffer mechanism 11 to be able to cut excess of yarn outside the yarn outlet in case of yarn loss.

The processing and control means of the system are configured to carry out the automatic self-thread operation including the steps of; i. supplying a signal to the drive means of the robotic arm 7 for the robotic arm 7 to position the yarn inlet 8 of the yarn handling tool 6 in correspondence with the yarn outlet of the yarn buffer mechanism 11 , ii. supplying an activation signal to the yarn cutter to cut excess of yarn outside the yarn outlet, iii. supplying an activation signal to the air blowing means of the yarn feeding device 10 to blow the free end of auxiliary yarn 1 on outside the yarn outlet of the yarn buffer mechanism 11 while retaining in place the auxiliary yarn 1 of the yarn buffer on outside the yarn outlet, and iv. supplying an activation signal to the yarn propelling means of the yarn handling tool 6 for said free end of auxiliary yarn 1 of the yarn buffer to be suctioned along the yarn conveying path inside the yarn handling tool 6.

The air blowing means comprise a Venturi tube and air injector assembly arranged to blow or inject air into the yarn outlet of the yarn buffer mechanism 11 upon receiving a signal from the processing a control means of the system.

Summarizing, the present invention provides a system and method for piecing a free end of auxiliary yarn 1 that, in contrast to the known piecing methods, provides high reliability and preciseness of both threading and piecing operations. Besides, the claimed method and system significantly improve the handling of the auxiliary yarn 1 by the facts that; prevent formation of curls and twists of auxiliary yarn outside the yarn handling tool 6, allow preparing and supplying a precise predetermined length of auxiliary yarn 1 to be propelled, increase the success rate of the auxiliary yarn 1 being caught by the revolving spindle tube 2 at a launching step of the piecing cycle, reduce the average time for the auxiliary yarn 1 to be caught by the revolving spindle tube 2, and/or allow an automatic self-threading procedure in case of yarn loss in the yarn path inside the yarn handling tool 6.

A person skilled in the art could introduce changes and modifications in the embodiments described without departing from the scope of the invention as it is defined in the attached claims. For example, although it has been disclosed a yarn piecing system and method wherein the step of supplying liquid to wet the yarn contact area of the revolving spindle tube is disclosed in combination with the use of a yarn handling tool and a yarn feeding device arranged along the path outside the yarn handling tool, a different yarn piecing system and method may be claimed that dispenses with the use of a yarn handling tool and robotic arm but still provided with liquid supplying means arranged to wet a yarn contact area of the revolving spindle tube. Likewise, although the yarn handling tool 6 has been disclosed attached to a robotic arm 7, it would be possible for the yarn handling tool 6 to be attached to automatic handling means other than a robotic arm 7 on condition that the automatic handling means allow handling the yarn nozzle and the yarn holding means to carry out threading.

Claims

1. A yarn piecing system for threading and piecing auxiliary yarn (1) at a spinning station of a ring spinning machine requiring repairment, comprising; a yarn handling tool (6) attached to a computer-controlled mechanical arm or robotic arm (7), drive means for the robotic arm (7), a yarn conveying path inside the yarn handling tool (6) for conveying auxiliary yarn (1) from a yarn inlet (8) to a yarn outlet, a yarn nozzle (9) on the yarn outlet of the yarn handling tool (6),

- yarn holding means (16) arranged on the yarn handling tool (6) to be able to form a threading section of auxiliary yarn (1) on outside the yarn nozzle (9), and processing and control means configured to provide an activation signal to the drive means of the robotic arm (7) for the yarn handling tool (6) to carry out threading and piecing operations once the free end of auxiliary yarn (1) is wrapped onto a revolving spindle tube (2) and rotation of the revolving spindle tube (2) is stopped, wherein the system further comprises; a yarn conveying path outside the yarn handling tool (6) for conveying auxiliary yarn (1) from an auxiliary yarn source to the yarn inlet (8) of the yarn handling tool (6), and a yarn feeding device (10) arranged and configured for feeding a length (“L0”, “L1”) of auxiliary yarn (1) to the yarn conveying path outside the yarn handling tool (6) during operation of the yarn handling tool (6) by the robotic arm (7).

2. A yarn piecing system according to claim 1 , wherein the yarn feeding device (10) comprises; a yarn buffer mechanism (11) to form a yarn buffer of auxiliary yarn (1) along the yarn conveying path outside the yarn handling tool (6) in between the yarn handling tool (6) and the auxiliary yarn source, and a control unit for the yarn buffer mechanism (11).

3. A yarn piecing system according to claim 2, wherein the yarn processing and control means are configured to supply a signal to the control unit of the yarn buffer mechanism (11) for the yarn buffer mechanism (11) to form the yarn buffer including a predetermined length (“L0”) of auxiliary yarn (1) at a launching step of the piecing cycle. A yarn piecing system according to any of claims 2 to 3, wherein the yarn buffer mechanism (11) comprises a yarn holding member (12) configured and arranged to hold the auxiliary yarn (1) of the yarn buffer under elastic tension while the auxiliary yarn (1) of the yarn buffer increases or reduces as the robotic arm (1) moves the yarn handling tool (6). A yarn piecing system according to claim 3, wherein the control unit for the yarn buffer mechanism (11) comprises a stepper motor (13) operationally connected to the yarn holding member (12) to keep the yarn holding member (12) to an elastic active working position while the auxiliary yarn (1) of the yarn buffer increases or reduces as the robotic arm (1) moves the yarn handling tool (6). A yarn piecing system according to any of claims 4 to 5, wherein the yarn holding member (12) comprises a yarn handling rod operationally connected to the control unit, said yarn handling rod being arranged to pivot an angle of rotation upon the control unit receives the signal from the processing and control means to form the yarn buffer. A yarn piecing system according to any of claims 2 to 6,

- wherein it comprises yarn propelling means (14) arranged along the yarn conveying path inside the yarn handling tool (6), and

- wherein the processing and control means are configured to supply an activation signal to the yarn propelling means (14) for said yarn propelling means (14) to propel the length of auxiliary yarn of the yarn buffer to the yarn nozzle (9) for the auxiliary yarn (1) of the yarn buffer to be wrapped onto a revolving spindle tube (2) at a yarn launching step of the piecing cycle. A yarn piecing system according to any of claims 1 to 7, comprising liquid supply means (15) arranged to be able to wet a yarn contact area of the revolving spindle tube (2) intended to be contacted by the free end of auxiliary yarn (1) at a yarn launching step of the piecing cycle. A yarn piecing system according to claim 8, wherein the processing and control means are configured to supply an activation signal to the liquid supply means (15) to supply liquid spray onto the yarn contact area of the revolving spindle tube (2) while the free end of auxiliary yarn (1) is propelled to the said yarn contact area of the revolving spindle tube (2). A yarn piecing system according to any of claims 1 to 9, wherein the yarn handling tool (6) is articulately attached to the robotic arm (7) by means of an articulated joint (21), said articulated joint (21) being configured to allow a tilting base (20) of the yarn handling tool (6) to pivot to an angled position to absorb heigh discrepancies of the working position of a movable support rail (3) of the ring spinning machine. A yarn piecing system according to claim 10, wherein said articulated joint (21) comprises an elastic connection arranged to allow the tilting base (20) of the yarn handling tool (6) to pivot to an angled position upon contacting the movable support rail (3), and to recover an initial resting position when ceasing contact with the movable support rail (3). A yarn piecing system according to any of claims 10 to 11 , comprising a tool angle sensor assembly (22) connected operatively to a controller unit of the robotic arm (7) to set the yarn handling tool (6) at an optimal working angled position upon contacting the movable support rail (3) at the spinning station requiring repairment. A yarn piecing system according to claim 12, wherein the tool angle sensor assembly (22) comprises a at least two proximity sensors (23, 24) for detecting presence of the tilting base (20) of the yarn handling tool (6), and wherein said controller unit is configured to check the status of the at least two proximity sensors (23, 24) and to supply a setting up signal to the processing and control means for said processing and control means order synchronization of movement of the robotic arm (7) with movement of the movable support rail (3) according to a calculated height offset value. A yarn piecing system according to any of claims 12 or 13, wherein the processing and control means are configured;

- to obtain an actual working height position of the movable support rail (3) at the spinning station requiring repairment based on the angled position of the yarn handling tool (6) provided by the controller unit of the robotic arm (7),

- to calculate a height offset value to be applied to height position data of the movable support rail (3) provided by a positioning sensor (19), and

- to send a signal to the controller unit of the robotic arm (7) to synchronize movement of the robotic arm (7) with movement of the movable support rail (3) based on the calculated height offset value. A yarn piecing system according to any of claims 1 to 14, comprising yarn cutter means (26) arranged on the yarn conveying path inside the yarn handling tool (6) for cutting auxiliary yarn inside the yarn handling tool (6) upon receiving a cutting signal from the processing and control means. A yarn piecing system according to any of claims 2 to 15, wherein the yarn feeding device (10) comprises; a yarn outlet of the yarn buffer mechanism (11),

- yarn retaining means arranged to retain in place a free end of auxiliary yarn (1) on outside the yarn outlet of the yarn buffer mechanism (11) in case of yarn loss, and air blowing means arranged to inject air into a yarn outlet of the yarn buffer mechanism (11),

- wherein in case of yarn loss along the yarn conveying path inside the yarn handling tool (6), the processing and control means are configured to carry out an automatic self-thread operation including the steps of; i. supplying a signal to the drive means of the robotic arm (7) for the robotic arm (7) positions the yarn inlet (8) of the yarn handling tool (6) in correspondence with the yarn outlet of the yarn buffer mechanism (11), ii. supplying an activation signal to the air blowing means of the yarn feeding device (10) to blow the free end of auxiliary yarn (1) on outside the yarn outlet of the yarn buffer mechanism (11) while retaining in place the auxiliary yarn (1) of the yarn buffer on outside the yarn outlet, and iii. supplying an activation signal to the yarn propelling means (14) of the yarn handling tool (6) for said free end of auxiliary yarn (1) of the yarn buffer to be suctioned along the yarn conveying path inside the yarn handling tool (6). A yarn piecing system according to claim 16, wherein the yarn feeding device (10) further comprises a yarn cutter connected operatively with the yarn outlet of the yarn buffer mechanism (11) to be able to cut excess of yarn outside the yarn outlet in case of yarn loss. A yarn piecing system according to any of claims 1 to 17, comprising image capture means (29) arranged preferably on the yarn handling tool (6) wherein the image capture means (29) are operatively connected to an artificial vision system configured to check whether there are impediments to do the piecing before the piecing cycle starts. A method of piecing auxiliary yarn (1) at a spinning station of a ring spinning machine requiring repairment, comprising the steps of; a) feeding a first length (“L0”) of auxiliary yarn (1) to a yarn conveying path outside a yarn handling tool (6) driven by a robotic arm, b) approaching the yarn handling tool (6) to a revolving spindle tube (2) requiring repairment, c) propelling the first length (“L0”) of auxiliary yarn (1) to a yarn nozzle (9) of the yarn handling tool (6) for a free end of the auxiliary yarn (1) to be wrapped onto the revolving spindle tube (2), d) after the free end of auxiliary yarn is wrapped onto the revolving spindle tube (2), stopping rotation of the revolving spindle, e) after step d), feeding a second length (“L1”) of auxiliary yarn (1) to the yarn conveying path outside the yarn handling tool (6) and increasing or reducing said second length (“L1”) of auxiliary yarn (1) while the robotic arm (7) moves the yarn handling tool (6) to carry out threading and piecing. A method of piecing auxiliary yarn according to claim 19, wherein; step a) comprises forming a yarn buffer including the first length (“L0”) of auxiliary yarn (1) along a yarn conveying path outside the yarn handling tool (6), step c) comprises propelling the first length (“L0”) of auxiliary yarn (1) of the yarn buffer to a yarn nozzle (9) of the yarn handling tool (6) for the free end of auxiliary yarn (1) of the yarn buffer to be wrapped onto the revolving spindle tube (2), and step e) comprises; i. forming a yarn buffer including the second length (“L1”) of auxiliary yarn (1), and ii. holding the second length (“L1”) of auxiliary yarn (1) of the yarn buffer under elastic tension while said second length (“L1”) of auxiliary yarn increases or reduces as the robotic arm (7) moves the yarn handling tool (6) to carry out threading and piecing. A method of piecing auxiliary yarn according to any of claims 19 to 20, wherein before or simultaneously to step c), it comprises the step of supplying liquid spray onto a yarn contact area of the revolving spindle tube (2) intended to be contacted by the free end of the first length (“L0”) of auxiliary yarn (1).