A yarn piecing system and method for piecing auxiliary yarn at a spinning station of a ring spinning machine

Abstract

A yarn piecing system and method for piecing auxiliary yarn at a spinning station of a ring spinning machine, comprising yarn supplying means for supplying a free end of auxiliary yarn (12), yarn fastening means (11) for fastening auxiliary yarn (12) on outside the yarn feeding nozzle (10) to form a threading section ("S") of auxiliary yarn (12) and, automatic handling means (7) for handling the yarn supplying means and the yarn fastening means (11). The system is characterized in that said automatic handling means include a yarn handling tool (8) with a yarn feeding nozzle (10), and in that the system comprises air suction means (13) arranged to suction air into the yarn feeding nozzle (10), and processing and control means configured to supply an activation signal to said air suction means in order to suction air into the yarn feeding nozzle (10).

Description

[0001] 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

[0002] 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 displaceably along a row of spinning stations with an option of stopping at a selected spinning station requiring a service operation.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] JP03199436A discloses one of said known yarn piecing systems having an automatic service station positionable 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.

[0007] 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 acting on the auxiliary yarn on outside the yarn feeding nozzle and preventing 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.

[0008] US 3,905,187A discloses a textile yarn piecing apparatus having a servicing assembly positionable in a first location for supplying a free end of auxiliary yarn from an auxiliary yarn bobbin to a revolving spindle having a bobbin onto which said free end is to be wrapped and a surrounding ring having a traveller which is to be threaded onto said auxiliary yarn. The servicing assembly is positionable in a second location for piecing an intermediate portion of said auxiliary yarn to roving issuing from roving delivery rolls and cutting the auxiliary yarn to again provide a cut free end thereof. The servicing assembly has a yarn feeding tube for conveying of yarn from the auxiliary yarn bobbin and an air suction yarn storage tube for storing a substantial length of the free end of the auxiliary yarn. The mouth openings of the yarn feeding and storage tubes are spaced from one another to provide a free yarn zone therebetween. There is also provided a yarn release airjet adjacent the free yarn zone, in the first location providing a release jet of air for removing the free end of yarn from the storage tube and propelling it toward the bobbin for wrapping therearound. The air suction yarn storage tube in the second location provides air suction for retrieving the cut free and of auxiliary yarn and storing it in the storage tube.

[0009] US 3,905,187A has the drawback that requires two assemblies for yarn handling; threading and piecing. Besides, both operations take place keeping the spindle tube rotating to keep the auxiliary yarn at an appropriate tension.

[0010] 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 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

[0011] 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 according to claim 1.

[0012] Thanks to the claimed features, the present invention provides a piecing system wherein suction of air takes place into the yarn feeding nozzle itself, which is used for supplying the free end of auxiliary yarn. Thus, the auxiliary yarn on outside the yarn feeding nozzle can be kept at an appropriate tension during threading and piecing without rotating the spindle tube and winding of auxiliary yarn from the auxiliary source. In this manner, reliability of both threading and piecing operations is significantly improved.

[0013] Besides, in the claimed system, the yarn feeding nozzle is mounted on a yarn handling tool suitable to handle yarn fastening means, for example a gripping element, involved in forming the threading section on outside the yarn feeding nozzle. Hence, preciseness on yarn handling is highly increased since both threading and piecing operations can be carried out with the same handling tool.

[0014] For one embodiment, the yarn supplying means of the yarn piecing system further comprise; air blowing means arranged to inject or blow air into the yarn feeding nozzle, and yarn retaining means configured to retain in place a predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle at the beginning of the piecing cycle, before the free end is wrapped onto the surface of the revolving spindle tube, and the processing and control means are configured to supply an activation signal to said air blowing means to blow the free end of said predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle while the yarn handling tool approaches the revolving spindle tube.

[0015] By virtue of the presence of said yarn retaining means, a predetermined length (L0) of auxiliary yarn can be retained in place on outside the yarn feeding nozzle at the beginning of the piecing cycle. Preferably, the retaining means are configured to retain in place a section of yarn by contact with a slipping plate. By blowing air into the yarn feeding nozzle, the free end of the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle can be positioned tangentially to the surface of the revolving spindle tube, while the yarn handling tool is approaching the revolving spindle. In this manner, the chance of adherence of the free end onto the surface of the revolving spindle tube is increased.

[0016] Besides, in contrast to the known yarn piecing systems which eject or propel the yarn toward the revolving spindle tube for wrapping there around, the claimed system does not propel or eject auxiliary yarn but it just blows a predetermined length of auxiliary yarn retained in place on outside the yarn feeding nozzle. This predetermined length of auxiliary yarn can be made oscillated tangentially to the surface of the revolving spindle tube to facilitate adherence of the free end of yarn by oscillating the yarn handling tool attached to the automatic handling means. Once the free end of auxiliary yarn is adhered onto the surface of the revolving spindle tube, the pulling force of the yarn running around the spindle tube disables retention of yarn by lifting the slipping plate.

[0017] According to one embodiment, the yarn fastening means of the yarn piecing system comprise at least one gripping element for fastening the auxiliary yarn on outside the yarn feeding nozzle, and preferably, said at least one gripping element is arranged on the yarn handling tool to allow the yarn handling tool to form the threading section of auxiliary yarn.

[0018] By gripping element, it shall be understood to mean an element for holding or grasping the yarn on outside the yarn feeding nozzle. This gripping element may be configured as a protrusion or nipple attached to the yarn handling tool, configured or adapted to hold or grasp a portion of yarn on outside the yarn feeding nozzle.

[0019] Advantageously, both the yarn fastening means, e.g. the at least one gripping element, and the yarn feeding nozzle are integrally attached to an end part of a frame structure of the yarn handling tool.

[0020] For one embodiment, the end part of the frame structure is configured as a tolerance absorbing structure in order for said end part to bend or flex to absorb operating tolerances of the yarn piecing system. For example, the end part frame structure includes a flexible metal strap.

[0021] By virtue of the provision of this flexible end part frame structure, the claimed yarn piecing system prevents the automatic handling means from automatic stopping if either the yarn feeding nozzle or the gripping element collide accidentally with the ring rail. Moreover, it has been found that this flexible end part frame structure constituting a tolerance absorbing structure helps reducing failure of the threading operation in case the handling tool does not position in the correct place.

[0022] Preferably, the automatic handling means comprise a robotic arm for handling the yarn handling tool. Advantageously, said robotic arm has at least six degrees of freedom of motion to allow the yarn fastening means, e.g. the at least one gripping element, to fasten the auxiliary yarn on outside the yarn feeding nozzle to form a threading section of auxiliary yarn.

[0023] In the claimed system, the handling tool is attached to a robotic arm, and the processing and control means are configured to provide a motion signal to the robotic arm; to allow the yarn fastening means, for example the at least one gripping element integrally attached to the handling tool, to fasten the auxiliary yarn on outside the yarn feeding nozzle to form the threading section, and to position the threading section of yarn at the flange of the ring for said threading section to be threaded into the ring traveller.

[0024] Thanks to these features, the threading and piecing operations can be carried out by using only one handling tool attached to the robotic arm, wherein the yarn feeding nozzle and the yarn fastening means are attached, preferably, integrally attached, to the handling tool mounted on the robotic arm.

[0025] According to one embodiment of the system, the air suction means comprise a first Venturi tube and air injector assembly arranged to suction air into the yarn feeding nozzle, upon receiving an activation signal from the processing and control means.

[0026] This first Venturi tube and air injector assembly are mounted on the handling tool, and preferably, it is arranged so that the Venturi tube is substantially aligned with the yarn feeding nozzle.

[0027] For a preferred embodiment, the air blowing means comprise a second Venturi tube and air injector assembly arranged to blow or inject air into the yarn feeding nozzle, upon receiving an activation signal from the processing and control means.

[0028] This second Venturi tube and air injector assembly are also mounted on the handling tool, preferably, mounted substantially aligned with the first Venturi tube and with the yarn feeding nozzle.

[0029] For one embodiment, the Venturi tubes of said first and / or said second Venturi tube and air injector assemblies are configured and arranged so that the auxiliary yarn passes along the Venturi tubes before being supplied through the yarn feeding nozzle.

[0030] Advantageously, the yarn retaining means are arranged in between the first and second Venturi tubes and air injector assemblies. In particular, they are arranged in a rear position with respect to the second Venturi tube and injector assembly and with respect to the yarn feeding nozzle.

[0031] This configuration has been found to be very efficient for precisely controlling not only the feeding but also the handling of auxiliary yarn through the yarn feeding nozzle of the handling tool.

[0032] Preferably, the yarn retaining means comprise a spring loaded slipping plate to retain in place by contact against a second plate the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle, and a piston and cylinder assembly arranged to actuate at least a compression spring against the slipping plate.

[0033] Once the free end of auxiliary yarn is adhered onto the surface of the revolving spindle tube, the pulling force of the yarn being wound disables retention of the yarn by lifting the spring loaded slipping plate. Thus, a further length of auxiliary yarn is fed through the yarn feeding nozzle for being wound around the spindle tube. The spring loaded slipping plate is configured to allow slippage of the yarn without causing breakage of yarn.

[0034] For one embodiment of the system, the processing and control means of the claimed system are configured; to supply a signal to actuate the piston and cylinder assembly of said yarn retaining means to free the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle after a predetermined time has elapsed without the free end of auxiliary being adhered onto the spindle tube, to supply a signal to the automatic handling means to position rearwardly and / or forwardly the yarn feeding nozzle of the handling tool with respect to the auxiliary yarn for a second predetermined length of auxiliary yarn to be on outside the yarn feeding nozzle, and to supply a signal to the piston and cylinder assembly of said yarn retaining means to retain in place the second predetermined length of auxiliary yarn on outside the yarn feeding nozzle at the beginning of the piecing cycle.

[0035] Advantageously, according to the same embodiment, the processing and control means are further configured to supply an activation signal to said air blowing means to blow the free end of said second predetermined length of auxiliary yarn on outside the yarn feeding nozzle while the yarn handling tool approaches the revolving spindle.

[0036] It has been found that a different length of auxiliary yarn may be suitable to approach the revolving spindle at the beginning of the piecing cycle. Depending on the type of yarn to be adhered onto the surface of the spindle tube as well as on the friction coefficient of the surface onto which the yarn is to be wrapped, a longer or shorter predetermined length of auxiliary yarn is required. The claimed features allow optimizing both the time expended and the quality of the wrapping operation.

[0037] For an embodiment, the yarn handling tool comprises; a frame structure configured to be attached to the automatic handling means, an end part of said frame structure, the yarn feeding nozzle attached to the end part of the frame structure to supply a free end of auxiliary yarn, the fastening means attached to the end part of the frame structure for fastening auxiliary yarn on outside the yarn feeding nozzle, the air suction means arranged to suction air into the yarn feeding nozzle, and preferably, the air blowing means arranged to inject air into the yarn feeding nozzle and, the yarn retaining means configured to retain in place a predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle.

[0038] Again preferably, the yarn fastening means, e.g. at least one gripping element, and the yarn feeding nozzle are integrally attached to the end part of the frame structure of the handling tool and, advantageously, the end part of the frame structure is a tolerance absorbing structure configured to bend or flex to absorb operating tolerances of the yarn piecing system.

[0039] For one embodiment, the air suction means comprise a first Venturi tube and air injector assembly arranged on the handling tool to suction air into the yarn feeding nozzle, upon receiving an activation signal coming from processing and control means of the yarn piecing system.

[0040] Advantageously, the air blowing means comprise a second Venturi tube and air injector assembly arranged on the handling tool to blow or inject air into the yarn feeding nozzle, upon receiving an activation signal coming from processing and control means of the yarn piecing system.

[0041] Again advantageously, the Venturi tubes of said first and / or said second Venturi tube and air injector assemblies are configured and arranged so that the auxiliary yarn passes along the Venturi tubes before being supplied through the yarn feeding nozzle.

[0042] For a preferred embodiment, the yarn retaining means are arranged on the handling tool in between the air suctioning means and the air blowing means. In particular, in between the first and second Venturi tubes and air injector assemblies.

[0043] This configuration has been found to be very efficient for precisely controlling not only the feeding but also the handling of auxiliary yarn through the yarn feeding nozzle of the handling tool.

[0044] Preferably, the yarn retaining means comprise a spring loaded slipping plate to retain in place by contact against a second plate the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle, and a piston and cylinder assembly arranged to actuate at least a compression spring against the slipping plate.

[0045] Advantageously, the handling tool further comprises an air conduct arranged to propel air to the ring of the spinning machine to cause deliberate motion of the ring traveller on the flange of the ring during the threading operation.

[0046] A second aspect of the present invention concerns a method for piecing auxiliary yarn at a spinning station of a ring spinning machine according to claim 15.

[0047] Thanks to the claimed features, the present invention provides a method for piecing a free end of auxiliary yarn that, in contrast to the known piecing methods, allows the threading and piecing operations take place at an appropriate tension of the yarn, without sagging, and without rotating the spindle tube. In this manner, reliability and preciseness of both threading and piecing operations is significantly improved.

[0048] Besides, the claimed method significantly simplifies the piecing process since threading and piecing operations can be carried out with only one yarn handling tool, preferably, one yarn handling tool attachable to a robotic arm. Advantageously, a robotic arm with at least six degrees of freedom of motion. Most of the known methods require more than one yarn handling tool to carry out both threading and piecing operations. Consequently, control and synchronization of several yarn handling tools is required in the prior art systems.

[0049] Another advantage of the claimed method is that it 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.

[0050] As previously stated, 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 doffing when 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.

[0051] For one embodiment of the method, step a) comprises retaining in place a predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle, and step b) comprises blowing air into the yarn feeding nozzle to position the predetermined length (L0) of auxiliary yarn tangentially to the spindle tube for aiding wrapping.

[0052] In contrast to the known methods, the claimed method does not eject the free end of auxiliary yarn towards the revolving spindle but a predetermined length of auxiliary yarn approaches to the revolving spindle on outside the yarn feeding nozzle. The predetermined length of auxiliary yarn is retained in place by means of yarn retaining means arranged on the yarn handling tool. This length of auxiliary yarn is positioned tangentially to the surface of the spindle tube by blowing air into the yarn feeding nozzle to aid wrapping.

[0053] Preferably, step b) comprises the step of moving in an oscillating manner the yarn handling tool, while blowing air into the yarn feeding nozzle for said length of auxiliary yarn is positioned tangentially to the surface of the spindle tube at different tube heights.

[0054] It has been found that the chance the free end of the auxiliary yarn is wrapped onto the surface of the spindle tube is increased significantly with this oscillating movement.

[0055] For one embodiment, in step e), the step of fastening the auxiliary yarn on outside the yarn feeding nozzle to form the threading section of auxiliary yarn, comprises fastening a portion of auxiliary yarn by fastening means, e.g. at least one gripping element, integrally attached to the yarn handling tool.

[0056] Hence, according to a preferred embodiment of the claimed method, only one yarn handling tool is responsible for creating the threading section "S" of auxiliary yarn on outside the yarn feeding nozzle, and for handling the threading section at the flange of the ring for said threading section is threaded into the ring traveller of the ring spinning machine. Precise motion of the yarn handling tool is required for said yarn handling tool causes the gripping element to hold or grasp the auxiliary yarn on outside the yarn feeding nozzle. Preferably, a robotic arm where the yarn handling tool is attached to is used for handling the yarn handling tool.

[0057] Advantageously, the claimed method comprises the step of cutting the auxiliary yarn after the piecing operation of step e) to provide a cut free end of auxiliary yarn, said cutting step including positioning the yarn handling tool at a predetermined distance from a cutting tool to obtain the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle.

[0058] Hence, after the auxiliary yarn is pieced with the roving issuing the drafting rollers, the handling tool is positioned with respect to the cutting tool to allow the cutting tool to cut the auxiliary yarn on outside the yarn feeding nozzle at a position suitable for obtaining one of the predetermined length (L0) of auxiliary yarn. In this manner, the system keeps ready to start a new piecing cycle at a new spinning station where breakage of yarn is detected.

[0059] In the present invention; By threading operation shall be understood the operation of creating or forming a threading section "S" of auxiliary yarn on outside the yarn feeding nozzle, and handling the threading section "S" at the flange of the ring of the ring spinning machine for said threading section "S" is threaded into the ring traveller of the ring spinning machine.

[0060] 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.

[0061] A piecing cycle of the claimed process and system shall be understood to include both threading and piecing operations.Brief description of the drawings

[0062] 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;

[0063] In detail: Figure 1 shows a perspective view of an embodiment of a yarn handling tool showing a predetermined length L0 of auxiliary yarn retained in place on outside the yarn feeding nozzle, and a gripping element and the yarn feeding nozzle integrally attached to a frame structure of the handling tool. Figure 2 shows the perspective view of the yarn handling tool of figure 1 where the free end of the predetermined length L0 of auxiliary yarn is blown on outside the yarn feeding nozzle while being retained in place by the yarn retaining means. Figure 3 is a schematic bottom view of the yarn handling tool of figure 1 showing respective Venturi tubes of the air suction means and air blowing means. The yarn retaining means are arranged in between those Venturi tubes. As it can be seen, the auxiliary yarn passes along the Venturi tubes before arriving to the yarn feeding nozzle. For the sake of clarity, this drawing does not show the air injectors arranged for injecting air into the Venturi tubes. Figure 4a is a schematic exploded view of the yarn handling tool of the embodiment of figure 1. Figure 4b shows another perspective view of the yarn handling tool of the embodiment of figure 1. Figure 5 shows a perspective view of a robotic arm where the yarn handling tool is attached for carrying out the yarn piecing system. For the sake of clarity, this drawing does not show the carriage arrangement on which the robotic arm is mounted displaceably along a row of spinning units of the ring spinning machine. The robotic arm can be stopped at a specific spinning unit in order to perform a service operation. Figure 6 shows a perspective view of the yarn handling tool attached to the robotic arm and approaching to an empty revolving spindle tube with the predetermined length L0 of yarn positioned tangentially to the surface of the spindle tube to aid wrapping. Figure 7 shows a perspective view of the yarn handling tool attached to the robotic arm and the robotic arm carrying a precise and particular motion to cause the gripping element to hold or grasp the auxiliary yarn on outside the yarn feeding nozzle to form the threading section of auxiliary yarn on outside the yarn feeding nozzle. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Figure 8 is a perspective view of the yarn handling tool attached to the robotic arm showing the threaded section "S" fastened in between the yarn feeding nozzle and the gripping element. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Figure 9 shows a perspective view of the yarn handling tool attached to the robotic arm while the threading section "S" 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. The threading operation takes place without stopping rotation of the spindle tube. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Figure 10 shows a schematic perspective view of the yarn handling tool attached to the robotic arm and positioned for threading the auxiliary yarn into the balloon constriction ring. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Figure 11 shows a schematic perspective view of the yarn handling tool attached to the robotic arm and positioned for piecing the auxiliary yarn on the roving issuing the front drafting rollers. For the sake of clarity, the roving is not shown and only the front drafting rollers of the drafting assembly have been represented. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Description of preferred embodiments

[0064] Following is a description of the claimed invention with reference to drawings of figures 1 to 11 representing an exemplary embodiment of the invention applicable to a ring spinning machine, which comprises a row of spinning stations arranged next to each other and a common ring rail (not shown) mounted displaceably up and down on the frame of the machine.

[0065] At each spinning station, a ring 1 is attached to the ring rail and a ring traveller 2 is movable mounted on a flange 3 of the ring 1. A revolving spindle (not shown) is arranged in the axial vertical axis of the ring 1. On the revolving spindle is placed a spindle tube 4 on which a package "P" of yarn is formed by spinning in a well-known manner, resulting in the formation of a cop. During spinning, the ring traveller 2 and the yarn threaded therein run round the spindle tube 4 on the flange 3 of the ring 1 for the yarn is wound onto the surface of the spindle tube 4. Arranged above the revolving spindle tube 4 is a balloon constriction ring 5, a yarn guide (not shown) and a drafting assembly including rear, middle and front drafting rollers from which drafted roving issues. Figure 11 shows the drafting assembly in a schematic way with only the front drafting rollers 6 of the drafting assembly.

[0066] Figure 5 shows a robotic arm 7 where a yarn handling tool 8 can be attached for carrying out the yarn piecing system and method. The robotic arm 7 is mounted displaceably along a row of spinning units (not shown) of the ring spinning machine. The claimed system includes processing and control means configured to supply a signal to the robotic arm 7 in order for the robotic arm 7 automatically to move along the row of spinning stations to a particular spinning position, when said processing and control means receive a signal from a sensor element detecting breakage of yarn at the corresponding spinning position. For the illustrated embodiment shown in figure 5, the robotic arm 7 has at least six degree of freedom of motion to allow the only one yarn handling tool 8 to create by itself the threading section "S" of auxiliary yarn 12.

[0067] As previously described, the present invention is directed to a yarn piecing system and method wherein the process of piecing takes place by supplying a free end 12a of auxiliary yarn 12 to a spindle tube 4 of a revolving spindle. Thus, the claimed system and method does not deal with piecing broken ends of yarn but it deals with piecing a free end 12a of auxiliary yarn 12 onto a revolving spindle tube 4.

[0068] The yarn handling tool 8 is configured to be attached to the robotic arm 7. In the embodiment shown in figures 1 to 4a, 4b, this yarn handling tool 8 includes a frame structure 9 attachable to the robotic arm 7, and a yarn feeding nozzle 10 and a gripping element 11 attached to an end part 9a of said frame structure 9. In the illustrated embodiments, the gripping element 11 and the yarn feeding nozzle 10 are integrally attached to the handling tool 8.

[0069] The yarn feeding nozzle 10 is intended for supplying the free end 12a of auxiliary yarn 12 to the spindle tube 4 of a revolving spindle onto which said free end 12a of auxiliary yarn is to be wrapped. The gripping element 11 is intended for fastening the auxiliary yarn 12 on outside the yarn feeding nozzle 10 when the robotic arm 7 carries out a particular and precise motion to cause said gripping element 11 to hold or grasp the auxiliary yarn 12 and form a threading section "S" of auxiliary yarn 12.

[0070] For the illustrated embodiment, air suction means and air blowing means are also arranged on the yarn handling tool 8 to respectively allow suctioning air and injecting air into the yarn feeding nozzle 10.

[0071] Yarn retaining means configured to retain in place the predetermined length L0 of the auxiliary yarn 12 on outside the yarn feeding nozzle 10 are also arranged on the yarn handling tool 8 in between the air suctioning and blowing means.

[0072] According to a preferred embodiment, the air suction means comprise a first Venturi tube 13 and air injector assembly arranged on the yarn handling tool 8 to suction air into the yarn feeding nozzle 10, upon receiving an activation signal from the processing and control means of the claimed system. Likewise, the air blowing means comprise a second Venturi tube 14 and air injector assembly arranged on the yarn handling tool 8 to blow air into the yarn feeding nozzle 10, upon receiving an activation signal coming from the processing and control means of the same system. As represented schematically in the bottom view of the figure 3, the Venturi tubes 13, 14 are mounted substantially aligned with the yarn feeding nozzle 10 and they are configured and arranged so that the auxiliary yarn 12 passes along them before being supplied through the yarn feeding nozzle 10.

[0073] In between the first and second Venturi tubes 13, 14 and air injector assemblies, the yarn retaining means are mounted and configured to retain in place the predetermined length L0 of auxiliary yarn 12, before the free end 12a is wrapped onto the surface of the revolving spindle tube 4.

[0074] For the illustrated embodiment shown in detail in the exploded view of figure 4a, the yarn retaining means "R" comprise a spring loaded slipping plate 15 to retain in place by contact a predetermined length L0 of auxiliary yarn 12 against a second plate 19. It also comprises a piston and cylinder assembly 16 arranged to actuate a plurality of compression springs 17 against the slipping plate 15.

[0075] In contrast to the known systems and methods, the free end 12a of auxiliary yarn is not ejected towards the revolving spindle tube 4, but retained by the yarn retaining means "R" and positioned tangentially to the surface of the spindle tube 4 by blowing air into the yarn feeding nozzle 10 as shown in figures 2 and 6. Once the free end 12a of auxiliary yarn 12 is adhered onto the surface of the revolving spindle tube 4, the pulling force of the yarn running round the spindle tube 4 disables retention by lifting the spring loaded slipping plate 15. Thus, a further length of auxiliary yarn 12 is fed through the yarn feeding nozzle 10 for being wound around the spindle tube 4. The stroke of the piston and cylinder assembly 16 is configured to actuate the plurality of compression springs 17 against the slipping plate 15 so that slippage of the auxiliary yarn 12 takes place without causing breakage of yarn.

[0076] In the example disclosed, the end part 9a of the frame structure 9 of the yarn handling tool 8 is configured as a tolerance absorbing structure, which comprises a flexible metal strap 18 attached to two plates 20a, 20b, in order for the end part 9a of the frame structure 9 to bend or flex to absorb operating tolerances of the yarn piecing system. This way, the robotic arm 7 is prevented from stopping if either the yarn feeding nozzle 10 or the gripping element 11 collide accidentally with the ring rail of the ring spinning machine. Moreover, the tolerance absorbing structure helps reducing failure of the threading operation in case the robotic arm 7 does not position the yarn handling tool 8 in the correct place in correspondence with the movable ring rail.

[0077] Below follows the description of the claimed method for piecing auxiliary yarn with reference to the illustrated figures.

[0078] Once a breakage of yarn is detected at one spinning station of the ring spinning machine, the robotic arm 7 receives a signal from the processing and control means of the system to displace along the row of spinning stations and locate centred in front of the spindle tube 4 of the spinning station where yarn is broken.

[0079] In a first step, a predetermined length L0 of auxiliary yarn is supplied to the yarn feeding nozzle 10 and retained in place on outside the yarn feeding nozzle 10 by means of the spring loaded slipping plate 15 contacting a portion of auxiliary yarn 12 against the second plate 19 of the yarn retaining means "R".

[0080] Then, in a second step, air is injected into the second Venturi tube 14 and air injector assembly to blow the free end 12a of the auxiliary yarn 12 and position the length L0 of auxiliary yarn 12 aligned with the yarn feeding nozzle 10 (see, figure 2).

[0081] In a third step, the robotic arm 7 approaches the yarn handling tool 8 to the revolving spindle tube 4 so that the predetermined length L0 of auxiliary yarn 12 is positioned tangentially to the surface of the spindle tube 4 by blowing air into the yarn feeding nozzle 10 (see, figure 6). To ensure the free end 12a of auxiliary yarn is wrapped correctly onto the surface of the spindle tube 4, the yarn handling tool 8 is made to oscillate vertically for the length L0 of auxiliary yarn 12 to be positioned tangentially at different tube heights.

[0082] After a while without the free end 12a of the auxiliary yarn 12 wraps onto the surface of the spindle tube 4, the processing and control means supply a signal to actuate the piston and cylinder assembly 16 of the yarn retaining means to free the predetermined length L0 of auxiliary yarn 12 on outside the yarn feeding nozzle 10. Then, the robotic arm 7 is actuated to position rearwardly or forwardly the yarn feeding nozzle 10 of the handling tool 8 with respect to the auxiliary yarn 12 for a second predetermined length of auxiliary yarn to be on outside the yarn feeding nozzle 10. A new signal is supplied to actuate the piston and cylinder assembly 16 of the yarn retaining means "R" to retain this time in place the second predetermined length of auxiliary yarn 12 on outside the yarn feeding nozzle 10.

[0083] It has been found that the length L0 of the auxiliary yarn 12 to be retained outside the yarn feeding nozzle 10 may vary depending mainly on the friction coefficient of the surface onto which the yarn is to be wrapped. For example, a longer length L0 of auxiliary yarn 12 may be necessary for aiding wrapping yarn if the surface of the spindle tube 4 is empty of yarn, whereas a shortest length L0 is necessary if the surface onto which the free end 12a is to be wrapped has yarn package "P".

[0084] Wrapping of the free end 12a of auxiliary yarn 12 triggers stopping rotation of the spindle tube 4 and activation of the air suctioning means to suction air inside the yarn feeding nozzle 10. For the illustrated embodiment, the suctioning of air is carried out by injecting air into the first Venturi tube 13 and air injector assembly. Nevertheless, other well-known air suctioning means may be envisaged for suctioning air into the yarn feeding nozzle 10.

[0085] Figure 7 shows a perspective view of the yarn handling tool 8 attached to the robotic arm 7, and the robotic arm 7 carrying out a precise and particular motion to cause the gripping element 11 to hold or grasp the auxiliary yarn 12 on outside the yarn feeding nozzle 10 to form the threading section"S" (see, figure 8).

[0086] In the claimed system and method, the air suctioned inside the yarn feeding nozzle 10 (see, arrows) keeps the auxiliary yarn 12 at an appropriate tension and allows the yarn handling tool 8 to displace relative to the auxiliary yarn 12 for the gripping element 11 to hold or grasps the auxiliary yarn 12 on outside the yarn feeding nozzle 10.

[0087] In contrast to the known methods, the claimed method allows the threading and piecing operations to be carried out with only one yarn handling tool 8 attachable to a robotic arm 7. The processing and control means of the system are configured to provide a motion signal to the robotic arm 7 to position the threading section "S" at the flange 3 of the ring 1 for the threading section "S" to be threaded into the ring traveller 2 (see, figure 9).

[0088] As it is shown in figure 9, an air conduct 21 is arranged on the yarn handling tool 8 for propelling air (see, arrows) to the ring 1 to cause deliberate motion of the ring traveller 2 on the flange 3 of the ring 1 during the threading operation.

[0089] Once the auxiliary yarn is threaded into the ring traveller 2, the robotic arm 7 displaces and positions the yarn handling tool 8 for threading the auxiliary yarn 12 into the balloon constriction ring 5 (see figure 10). Then, the robotic arm 7 positions the yarn handling tool 8 so that the auxiliary yarn 12 on outside the yarn feeding nozzle 10 is pieced with the roving issuing the front drafting rollers 6 (see, figure 11). All these operations take place without the spindle tube 4 rotating to obtain maximum preciseness.

[0090] In a final step of the method, the robotic arm 7 positions the yarn handling tool 8 at a predetermined distance from a cutting tool (not represented) for said cutting tool cuts the auxiliary yarn 12 at a position configured to obtain anew the predetermined length L0 of auxiliary yarn 12 on outside the yarn feeding nozzle 10. The system is then ready for starting a new piecing cycle at a new spinning station where breakage of yarn is detected.

[0091] As previously stated, if during handling either the gripping element 11 or the yarn feeding nozzle 10 collides accidentally with the oscillating ring rail, the end part 9a of the frame structure 9 of the yarn handling tool 8 may bend or flex to allow components to reposition in order to avoid any failure or stopping of the robotic arm 7.

[0092] Summarizing, the present invention provides a system and method for piecing a free end 12a of auxiliary yarn 12 that, in contrast to the known piecing methods, provides high reliability and preciseness of both threading and piecing operations. Besides, the claimed method significantly simplifies the piecing process since threading and piecing operations may be carried out with only one yarn handling tool 8, preferably, one yarn handling tool 8 attachable to a robotic arm 7 with at least six degree of freedom of motion.

[0093] For an unillustrated embodiment, no robotic arm is used and the yarn fastening means are arranged on a second tool of the automatic handling means. In this case, the yarn handling tool would include; a frame structure 9 attachable to the automatic handling means, an end part 9a of said frame structure 9, a yarn feeding nozzle 10 attached to the end part 9a of the frame structure 9 to supply a free end 12a of auxiliary yarn 12, air suction means 13 arranged to suction air into the yarn feeding nozzle 10, and also preferably; air blowing means 14 arranged to inject air into the yarn feeding nozzle 10 and yarn retaining means "R" configured to retain in place a predetermined length "L0" of auxiliary yarn 12 on outside the yarn feeding nozzle 10.

[0094] In this unillustrated embodiment, the yarn fastening means could be configured as a pincer or suction tube attached on the second tool to fasten the auxiliary yarn 12 on outside the yarn feeding nozzle and help the yarn handling tool 8 to carry out the threading and piecing operations.

[0095] 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 an embodiment has been disclosed where the yarn fastening means are configured as a gripping element 11 attached to the yarn handling tool 8, it would be possible to provide another embodiment where the yarn fastening means were configured as a pincer, or as a suction tube, arranged on the claimed yarn handling tool, or on a different tool, of the automatic handling means.

Examples

Embodiment Construction

[0064]Following is a description of the claimed invention with reference to drawings of figures 1 to 11 representing an exemplary embodiment of the invention applicable to a ring spinning machine, which comprises a row of spinning stations arranged next to each other and a common ring rail (not shown) mounted displaceably up and down on the frame of the machine.

[0065]At each spinning station, a ring 1 is attached to the ring rail and a ring traveller 2 is movable mounted on a flange 3 of the ring 1. A revolving spindle (not shown) is arranged in the axial vertical axis of the ring 1. On the revolving spindle is placed a spindle tube 4 on which a package "P" of yarn is formed by spinning in a well-known manner, resulting in the formation of a cop. During spinning, the ring traveller 2 and the yarn threaded therein run round the spindle tube 4 on the flange 3 of the ring 1 for the yarn is wound onto the surface of the spindle tube 4. Arranged above the revolving spindle tube 4 is a ba...

[0001] 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

[0002] 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 displaceably along a row of spinning stations with an option of stopping at a selected spinning station requiring a service operation.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] JP03199436A discloses one of said known yarn piecing systems having an automatic service station positionable 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.

[0007] 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 acting on the auxiliary yarn on outside the yarn feeding nozzle and preventing 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.

[0008] US 3,905,187A discloses a textile yarn piecing apparatus having a servicing assembly positionable in a first location for supplying a free end of auxiliary yarn from an auxiliary yarn bobbin to a revolving spindle having a bobbin onto which said free end is to be wrapped and a surrounding ring having a traveller which is to be threaded onto said auxiliary yarn. The servicing assembly is positionable in a second location for piecing an intermediate portion of said auxiliary yarn to roving issuing from roving delivery rolls and cutting the auxiliary yarn to again provide a cut free end thereof. The servicing assembly has a yarn feeding tube for conveying of yarn from the auxiliary yarn bobbin and an air suction yarn storage tube for storing a substantial length of the free end of the auxiliary yarn. The mouth openings of the yarn feeding and storage tubes are spaced from one another to provide a free yarn zone therebetween. There is also provided a yarn release airjet adjacent the free yarn zone, in the first location providing a release jet of air for removing the free end of yarn from the storage tube and propelling it toward the bobbin for wrapping therearound. The air suction yarn storage tube in the second location provides air suction for retrieving the cut free and of auxiliary yarn and storing it in the storage tube.

[0009] US 3,905,187A has the drawback that requires two assemblies for yarn handling; threading and piecing. Besides, both operations take place keeping the spindle tube rotating to keep the auxiliary yarn at an appropriate tension.

[0010] 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 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

[0011] 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 according to claim 1.

[0012] Thanks to the claimed features, the present invention provides a piecing system wherein suction of air takes place into the yarn feeding nozzle itself, which is used for supplying the free end of auxiliary yarn. Thus, the auxiliary yarn on outside the yarn feeding nozzle can be kept at an appropriate tension during threading and piecing without rotating the spindle tube and winding of auxiliary yarn from the auxiliary source. In this manner, reliability of both threading and piecing operations is significantly improved.

[0013] Besides, in the claimed system, the yarn feeding nozzle is mounted on a yarn handling tool suitable to handle yarn fastening means, for example a gripping element, involved in forming the threading section on outside the yarn feeding nozzle. Hence, preciseness on yarn handling is highly increased since both threading and piecing operations can be carried out with the same handling tool.

[0014] For one embodiment, the yarn supplying means of the yarn piecing system further comprise; air blowing means arranged to inject or blow air into the yarn feeding nozzle, and yarn retaining means configured to retain in place a predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle at the beginning of the piecing cycle, before the free end is wrapped onto the surface of the revolving spindle tube, and the processing and control means are configured to supply an activation signal to said air blowing means to blow the free end of said predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle while the yarn handling tool approaches the revolving spindle tube.

[0015] By virtue of the presence of said yarn retaining means, a predetermined length (L0) of auxiliary yarn can be retained in place on outside the yarn feeding nozzle at the beginning of the piecing cycle. Preferably, the retaining means are configured to retain in place a section of yarn by contact with a slipping plate. By blowing air into the yarn feeding nozzle, the free end of the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle can be positioned tangentially to the surface of the revolving spindle tube, while the yarn handling tool is approaching the revolving spindle. In this manner, the chance of adherence of the free end onto the surface of the revolving spindle tube is increased.

[0016] Besides, in contrast to the known yarn piecing systems which eject or propel the yarn toward the revolving spindle tube for wrapping there around, the claimed system does not propel or eject auxiliary yarn but it just blows a predetermined length of auxiliary yarn retained in place on outside the yarn feeding nozzle. This predetermined length of auxiliary yarn can be made oscillated tangentially to the surface of the revolving spindle tube to facilitate adherence of the free end of yarn by oscillating the yarn handling tool attached to the automatic handling means. Once the free end of auxiliary yarn is adhered onto the surface of the revolving spindle tube, the pulling force of the yarn running around the spindle tube disables retention of yarn by lifting the slipping plate.

[0017] According to one embodiment, the yarn fastening means of the yarn piecing system comprise at least one gripping element for fastening the auxiliary yarn on outside the yarn feeding nozzle, and preferably, said at least one gripping element is arranged on the yarn handling tool to allow the yarn handling tool to form the threading section of auxiliary yarn.

[0018] By gripping element, it shall be understood to mean an element for holding or grasping the yarn on outside the yarn feeding nozzle. This gripping element may be configured as a protrusion or nipple attached to the yarn handling tool, configured or adapted to hold or grasp a portion of yarn on outside the yarn feeding nozzle.

[0019] Advantageously, both the yarn fastening means, e.g. the at least one gripping element, and the yarn feeding nozzle are integrally attached to an end part of a frame structure of the yarn handling tool.

[0020] For one embodiment, the end part of the frame structure is configured as a tolerance absorbing structure in order for said end part to bend or flex to absorb operating tolerances of the yarn piecing system. For example, the end part frame structure includes a flexible metal strap.

[0021] By virtue of the provision of this flexible end part frame structure, the claimed yarn piecing system prevents the automatic handling means from automatic stopping if either the yarn feeding nozzle or the gripping element collide accidentally with the ring rail. Moreover, it has been found that this flexible end part frame structure constituting a tolerance absorbing structure helps reducing failure of the threading operation in case the handling tool does not position in the correct place.

[0022] Preferably, the automatic handling means comprise a robotic arm for handling the yarn handling tool. Advantageously, said robotic arm has at least six degrees of freedom of motion to allow the yarn fastening means, e.g. the at least one gripping element, to fasten the auxiliary yarn on outside the yarn feeding nozzle to form a threading section of auxiliary yarn.

[0023] In the claimed system, the handling tool is attached to a robotic arm, and the processing and control means are configured to provide a motion signal to the robotic arm; to allow the yarn fastening means, for example the at least one gripping element integrally attached to the handling tool, to fasten the auxiliary yarn on outside the yarn feeding nozzle to form the threading section, and to position the threading section of yarn at the flange of the ring for said threading section to be threaded into the ring traveller.

[0024] Thanks to these features, the threading and piecing operations can be carried out by using only one handling tool attached to the robotic arm, wherein the yarn feeding nozzle and the yarn fastening means are attached, preferably, integrally attached, to the handling tool mounted on the robotic arm.

[0025] According to one embodiment of the system, the air suction means comprise a first Venturi tube and air injector assembly arranged to suction air into the yarn feeding nozzle, upon receiving an activation signal from the processing and control means.

[0026] This first Venturi tube and air injector assembly are mounted on the handling tool, and preferably, it is arranged so that the Venturi tube is substantially aligned with the yarn feeding nozzle.

[0027] For a preferred embodiment, the air blowing means comprise a second Venturi tube and air injector assembly arranged to blow or inject air into the yarn feeding nozzle, upon receiving an activation signal from the processing and control means.

[0028] This second Venturi tube and air injector assembly are also mounted on the handling tool, preferably, mounted substantially aligned with the first Venturi tube and with the yarn feeding nozzle.

[0029] For one embodiment, the Venturi tubes of said first and / or said second Venturi tube and air injector assemblies are configured and arranged so that the auxiliary yarn passes along the Venturi tubes before being supplied through the yarn feeding nozzle.

[0030] Advantageously, the yarn retaining means are arranged in between the first and second Venturi tubes and air injector assemblies. In particular, they are arranged in a rear position with respect to the second Venturi tube and injector assembly and with respect to the yarn feeding nozzle.

[0031] This configuration has been found to be very efficient for precisely controlling not only the feeding but also the handling of auxiliary yarn through the yarn feeding nozzle of the handling tool.

[0032] Preferably, the yarn retaining means comprise a spring loaded slipping plate to retain in place by contact against a second plate the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle, and a piston and cylinder assembly arranged to actuate at least a compression spring against the slipping plate.

[0033] Once the free end of auxiliary yarn is adhered onto the surface of the revolving spindle tube, the pulling force of the yarn being wound disables retention of the yarn by lifting the spring loaded slipping plate. Thus, a further length of auxiliary yarn is fed through the yarn feeding nozzle for being wound around the spindle tube. The spring loaded slipping plate is configured to allow slippage of the yarn without causing breakage of yarn.

[0034] For one embodiment of the system, the processing and control means of the claimed system are configured; to supply a signal to actuate the piston and cylinder assembly of said yarn retaining means to free the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle after a predetermined time has elapsed without the free end of auxiliary being adhered onto the spindle tube, to supply a signal to the automatic handling means to position rearwardly and / or forwardly the yarn feeding nozzle of the handling tool with respect to the auxiliary yarn for a second predetermined length of auxiliary yarn to be on outside the yarn feeding nozzle, and to supply a signal to the piston and cylinder assembly of said yarn retaining means to retain in place the second predetermined length of auxiliary yarn on outside the yarn feeding nozzle at the beginning of the piecing cycle.

[0035] Advantageously, according to the same embodiment, the processing and control means are further configured to supply an activation signal to said air blowing means to blow the free end of said second predetermined length of auxiliary yarn on outside the yarn feeding nozzle while the yarn handling tool approaches the revolving spindle.

[0036] It has been found that a different length of auxiliary yarn may be suitable to approach the revolving spindle at the beginning of the piecing cycle. Depending on the type of yarn to be adhered onto the surface of the spindle tube as well as on the friction coefficient of the surface onto which the yarn is to be wrapped, a longer or shorter predetermined length of auxiliary yarn is required. The claimed features allow optimizing both the time expended and the quality of the wrapping operation.

[0037] For an embodiment, the yarn handling tool comprises; a frame structure configured to be attached to the automatic handling means, an end part of said frame structure, the yarn feeding nozzle attached to the end part of the frame structure to supply a free end of auxiliary yarn, the fastening means attached to the end part of the frame structure for fastening auxiliary yarn on outside the yarn feeding nozzle, the air suction means arranged to suction air into the yarn feeding nozzle, and preferably, the air blowing means arranged to inject air into the yarn feeding nozzle and, the yarn retaining means configured to retain in place a predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle.

[0038] Again preferably, the yarn fastening means, e.g. at least one gripping element, and the yarn feeding nozzle are integrally attached to the end part of the frame structure of the handling tool and, advantageously, the end part of the frame structure is a tolerance absorbing structure configured to bend or flex to absorb operating tolerances of the yarn piecing system.

[0039] For one embodiment, the air suction means comprise a first Venturi tube and air injector assembly arranged on the handling tool to suction air into the yarn feeding nozzle, upon receiving an activation signal coming from processing and control means of the yarn piecing system.

[0040] Advantageously, the air blowing means comprise a second Venturi tube and air injector assembly arranged on the handling tool to blow or inject air into the yarn feeding nozzle, upon receiving an activation signal coming from processing and control means of the yarn piecing system.

[0041] Again advantageously, the Venturi tubes of said first and / or said second Venturi tube and air injector assemblies are configured and arranged so that the auxiliary yarn passes along the Venturi tubes before being supplied through the yarn feeding nozzle.

[0042] For a preferred embodiment, the yarn retaining means are arranged on the handling tool in between the air suctioning means and the air blowing means. In particular, in between the first and second Venturi tubes and air injector assemblies.

[0043] This configuration has been found to be very efficient for precisely controlling not only the feeding but also the handling of auxiliary yarn through the yarn feeding nozzle of the handling tool.

[0044] Preferably, the yarn retaining means comprise a spring loaded slipping plate to retain in place by contact against a second plate the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle, and a piston and cylinder assembly arranged to actuate at least a compression spring against the slipping plate.

[0045] Advantageously, the handling tool further comprises an air conduct arranged to propel air to the ring of the spinning machine to cause deliberate motion of the ring traveller on the flange of the ring during the threading operation.

[0046] A second aspect of the present invention concerns a method for piecing auxiliary yarn at a spinning station of a ring spinning machine according to claim 15.

[0047] Thanks to the claimed features, the present invention provides a method for piecing a free end of auxiliary yarn that, in contrast to the known piecing methods, allows the threading and piecing operations take place at an appropriate tension of the yarn, without sagging, and without rotating the spindle tube. In this manner, reliability and preciseness of both threading and piecing operations is significantly improved.

[0048] Besides, the claimed method significantly simplifies the piecing process since threading and piecing operations can be carried out with only one yarn handling tool, preferably, one yarn handling tool attachable to a robotic arm. Advantageously, a robotic arm with at least six degrees of freedom of motion. Most of the known methods require more than one yarn handling tool to carry out both threading and piecing operations. Consequently, control and synchronization of several yarn handling tools is required in the prior art systems.

[0049] Another advantage of the claimed method is that it 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.

[0050] As previously stated, 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 doffing when 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.

[0051] For one embodiment of the method, step a) comprises retaining in place a predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle, and step b) comprises blowing air into the yarn feeding nozzle to position the predetermined length (L0) of auxiliary yarn tangentially to the spindle tube for aiding wrapping.

[0052] In contrast to the known methods, the claimed method does not eject the free end of auxiliary yarn towards the revolving spindle but a predetermined length of auxiliary yarn approaches to the revolving spindle on outside the yarn feeding nozzle. The predetermined length of auxiliary yarn is retained in place by means of yarn retaining means arranged on the yarn handling tool. This length of auxiliary yarn is positioned tangentially to the surface of the spindle tube by blowing air into the yarn feeding nozzle to aid wrapping.

[0053] Preferably, step b) comprises the step of moving in an oscillating manner the yarn handling tool, while blowing air into the yarn feeding nozzle for said length of auxiliary yarn is positioned tangentially to the surface of the spindle tube at different tube heights.

[0054] It has been found that the chance the free end of the auxiliary yarn is wrapped onto the surface of the spindle tube is increased significantly with this oscillating movement.

[0055] For one embodiment, in step e), the step of fastening the auxiliary yarn on outside the yarn feeding nozzle to form the threading section of auxiliary yarn, comprises fastening a portion of auxiliary yarn by fastening means, e.g. at least one gripping element, integrally attached to the yarn handling tool.

[0056] Hence, according to a preferred embodiment of the claimed method, only one yarn handling tool is responsible for creating the threading section "S" of auxiliary yarn on outside the yarn feeding nozzle, and for handling the threading section at the flange of the ring for said threading section is threaded into the ring traveller of the ring spinning machine. Precise motion of the yarn handling tool is required for said yarn handling tool causes the gripping element to hold or grasp the auxiliary yarn on outside the yarn feeding nozzle. Preferably, a robotic arm where the yarn handling tool is attached to is used for handling the yarn handling tool.

[0057] Advantageously, the claimed method comprises the step of cutting the auxiliary yarn after the piecing operation of step e) to provide a cut free end of auxiliary yarn, said cutting step including positioning the yarn handling tool at a predetermined distance from a cutting tool to obtain the predetermined length (L0) of auxiliary yarn on outside the yarn feeding nozzle.

[0058] Hence, after the auxiliary yarn is pieced with the roving issuing the drafting rollers, the handling tool is positioned with respect to the cutting tool to allow the cutting tool to cut the auxiliary yarn on outside the yarn feeding nozzle at a position suitable for obtaining one of the predetermined length (L0) of auxiliary yarn. In this manner, the system keeps ready to start a new piecing cycle at a new spinning station where breakage of yarn is detected.

[0059] In the present invention; By threading operation shall be understood the operation of creating or forming a threading section "S" of auxiliary yarn on outside the yarn feeding nozzle, and handling the threading section "S" at the flange of the ring of the ring spinning machine for said threading section "S" is threaded into the ring traveller of the ring spinning machine.

[0060] 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.

[0061] A piecing cycle of the claimed process and system shall be understood to include both threading and piecing operations.Brief description of the drawings

[0062] 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;

[0063] In detail: Figure 1 shows a perspective view of an embodiment of a yarn handling tool showing a predetermined length L0 of auxiliary yarn retained in place on outside the yarn feeding nozzle, and a gripping element and the yarn feeding nozzle integrally attached to a frame structure of the handling tool. Figure 2 shows the perspective view of the yarn handling tool of figure 1 where the free end of the predetermined length L0 of auxiliary yarn is blown on outside the yarn feeding nozzle while being retained in place by the yarn retaining means. Figure 3 is a schematic bottom view of the yarn handling tool of figure 1 showing respective Venturi tubes of the air suction means and air blowing means. The yarn retaining means are arranged in between those Venturi tubes. As it can be seen, the auxiliary yarn passes along the Venturi tubes before arriving to the yarn feeding nozzle. For the sake of clarity, this drawing does not show the air injectors arranged for injecting air into the Venturi tubes. Figure 4a is a schematic exploded view of the yarn handling tool of the embodiment of figure 1. Figure 4b shows another perspective view of the yarn handling tool of the embodiment of figure 1. Figure 5 shows a perspective view of a robotic arm where the yarn handling tool is attached for carrying out the yarn piecing system. For the sake of clarity, this drawing does not show the carriage arrangement on which the robotic arm is mounted displaceably along a row of spinning units of the ring spinning machine. The robotic arm can be stopped at a specific spinning unit in order to perform a service operation. Figure 6 shows a perspective view of the yarn handling tool attached to the robotic arm and approaching to an empty revolving spindle tube with the predetermined length L0 of yarn positioned tangentially to the surface of the spindle tube to aid wrapping. Figure 7 shows a perspective view of the yarn handling tool attached to the robotic arm and the robotic arm carrying a precise and particular motion to cause the gripping element to hold or grasp the auxiliary yarn on outside the yarn feeding nozzle to form the threading section of auxiliary yarn on outside the yarn feeding nozzle. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Figure 8 is a perspective view of the yarn handling tool attached to the robotic arm showing the threaded section "S" fastened in between the yarn feeding nozzle and the gripping element. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Figure 9 shows a perspective view of the yarn handling tool attached to the robotic arm while the threading section "S" 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. The threading operation takes place without stopping rotation of the spindle tube. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Figure 10 shows a schematic perspective view of the yarn handling tool attached to the robotic arm and positioned for threading the auxiliary yarn into the balloon constriction ring. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Figure 11 shows a schematic perspective view of the yarn handling tool attached to the robotic arm and positioned for piecing the auxiliary yarn on the roving issuing the front drafting rollers. For the sake of clarity, the roving is not shown and only the front drafting rollers of the drafting assembly have been represented. The arrows next the yarn feeding nozzle graphically represent the air suctioning into the yarn feeding nozzle. Description of preferred embodiments

[0064] Following is a description of the claimed invention with reference to drawings of figures 1 to 11 representing an exemplary embodiment of the invention applicable to a ring spinning machine, which comprises a row of spinning stations arranged next to each other and a common ring rail (not shown) mounted displaceably up and down on the frame of the machine.

[0065] At each spinning station, a ring 1 is attached to the ring rail and a ring traveller 2 is movable mounted on a flange 3 of the ring 1. A revolving spindle (not shown) is arranged in the axial vertical axis of the ring 1. On the revolving spindle is placed a spindle tube 4 on which a package "P" of yarn is formed by spinning in a well-known manner, resulting in the formation of a cop. During spinning, the ring traveller 2 and the yarn threaded therein run round the spindle tube 4 on the flange 3 of the ring 1 for the yarn is wound onto the surface of the spindle tube 4. Arranged above the revolving spindle tube 4 is a balloon constriction ring 5, a yarn guide (not shown) and a drafting assembly including rear, middle and front drafting rollers from which drafted roving issues. Figure 11 shows the drafting assembly in a schematic way with only the front drafting rollers 6 of the drafting assembly.

[0066] Figure 5 shows a robotic arm 7 where a yarn handling tool 8 can be attached for carrying out the yarn piecing system and method. The robotic arm 7 is mounted displaceably along a row of spinning units (not shown) of the ring spinning machine. The claimed system includes processing and control means configured to supply a signal to the robotic arm 7 in order for the robotic arm 7 automatically to move along the row of spinning stations to a particular spinning position, when said processing and control means receive a signal from a sensor element detecting breakage of yarn at the corresponding spinning position. For the illustrated embodiment shown in figure 5, the robotic arm 7 has at least six degree of freedom of motion to allow the only one yarn handling tool 8 to create by itself the threading section "S" of auxiliary yarn 12.

[0067] As previously described, the present invention is directed to a yarn piecing system and method wherein the process of piecing takes place by supplying a free end 12a of auxiliary yarn 12 to a spindle tube 4 of a revolving spindle. Thus, the claimed system and method does not deal with piecing broken ends of yarn but it deals with piecing a free end 12a of auxiliary yarn 12 onto a revolving spindle tube 4.

[0068] The yarn handling tool 8 is configured to be attached to the robotic arm 7. In the embodiment shown in figures 1 to 4a, 4b, this yarn handling tool 8 includes a frame structure 9 attachable to the robotic arm 7, and a yarn feeding nozzle 10 and a gripping element 11 attached to an end part 9a of said frame structure 9. In the illustrated embodiments, the gripping element 11 and the yarn feeding nozzle 10 are integrally attached to the handling tool 8.

[0069] The yarn feeding nozzle 10 is intended for supplying the free end 12a of auxiliary yarn 12 to the spindle tube 4 of a revolving spindle onto which said free end 12a of auxiliary yarn is to be wrapped. The gripping element 11 is intended for fastening the auxiliary yarn 12 on outside the yarn feeding nozzle 10 when the robotic arm 7 carries out a particular and precise motion to cause said gripping element 11 to hold or grasp the auxiliary yarn 12 and form a threading section "S" of auxiliary yarn 12.

[0070] For the illustrated embodiment, air suction means and air blowing means are also arranged on the yarn handling tool 8 to respectively allow suctioning air and injecting air into the yarn feeding nozzle 10.

[0071] Yarn retaining means configured to retain in place the predetermined length L0 of the auxiliary yarn 12 on outside the yarn feeding nozzle 10 are also arranged on the yarn handling tool 8 in between the air suctioning and blowing means.

[0072] According to a preferred embodiment, the air suction means comprise a first Venturi tube 13 and air injector assembly arranged on the yarn handling tool 8 to suction air into the yarn feeding nozzle 10, upon receiving an activation signal from the processing and control means of the claimed system. Likewise, the air blowing means comprise a second Venturi tube 14 and air injector assembly arranged on the yarn handling tool 8 to blow air into the yarn feeding nozzle 10, upon receiving an activation signal coming from the processing and control means of the same system. As represented schematically in the bottom view of the figure 3, the Venturi tubes 13, 14 are mounted substantially aligned with the yarn feeding nozzle 10 and they are configured and arranged so that the auxiliary yarn 12 passes along them before being supplied through the yarn feeding nozzle 10.

[0073] In between the first and second Venturi tubes 13, 14 and air injector assemblies, the yarn retaining means are mounted and configured to retain in place the predetermined length L0 of auxiliary yarn 12, before the free end 12a is wrapped onto the surface of the revolving spindle tube 4.

[0074] For the illustrated embodiment shown in detail in the exploded view of figure 4a, the yarn retaining means "R" comprise a spring loaded slipping plate 15 to retain in place by contact a predetermined length L0 of auxiliary yarn 12 against a second plate 19. It also comprises a piston and cylinder assembly 16 arranged to actuate a plurality of compression springs 17 against the slipping plate 15.

[0075] In contrast to the known systems and methods, the free end 12a of auxiliary yarn is not ejected towards the revolving spindle tube 4, but retained by the yarn retaining means "R" and positioned tangentially to the surface of the spindle tube 4 by blowing air into the yarn feeding nozzle 10 as shown in figures 2 and 6. Once the free end 12a of auxiliary yarn 12 is adhered onto the surface of the revolving spindle tube 4, the pulling force of the yarn running round the spindle tube 4 disables retention by lifting the spring loaded slipping plate 15. Thus, a further length of auxiliary yarn 12 is fed through the yarn feeding nozzle 10 for being wound around the spindle tube 4. The stroke of the piston and cylinder assembly 16 is configured to actuate the plurality of compression springs 17 against the slipping plate 15 so that slippage of the auxiliary yarn 12 takes place without causing breakage of yarn.

[0076] In the example disclosed, the end part 9a of the frame structure 9 of the yarn handling tool 8 is configured as a tolerance absorbing structure, which comprises a flexible metal strap 18 attached to two plates 20a, 20b, in order for the end part 9a of the frame structure 9 to bend or flex to absorb operating tolerances of the yarn piecing system. This way, the robotic arm 7 is prevented from stopping if either the yarn feeding nozzle 10 or the gripping element 11 collide accidentally with the ring rail of the ring spinning machine. Moreover, the tolerance absorbing structure helps reducing failure of the threading operation in case the robotic arm 7 does not position the yarn handling tool 8 in the correct place in correspondence with the movable ring rail.

[0077] Below follows the description of the claimed method for piecing auxiliary yarn with reference to the illustrated figures.

[0078] Once a breakage of yarn is detected at one spinning station of the ring spinning machine, the robotic arm 7 receives a signal from the processing and control means of the system to displace along the row of spinning stations and locate centred in front of the spindle tube 4 of the spinning station where yarn is broken.

[0079] In a first step, a predetermined length L0 of auxiliary yarn is supplied to the yarn feeding nozzle 10 and retained in place on outside the yarn feeding nozzle 10 by means of the spring loaded slipping plate 15 contacting a portion of auxiliary yarn 12 against the second plate 19 of the yarn retaining means "R".

[0080] Then, in a second step, air is injected into the second Venturi tube 14 and air injector assembly to blow the free end 12a of the auxiliary yarn 12 and position the length L0 of auxiliary yarn 12 aligned with the yarn feeding nozzle 10 (see, figure 2).

[0081] In a third step, the robotic arm 7 approaches the yarn handling tool 8 to the revolving spindle tube 4 so that the predetermined length L0 of auxiliary yarn 12 is positioned tangentially to the surface of the spindle tube 4 by blowing air into the yarn feeding nozzle 10 (see, figure 6). To ensure the free end 12a of auxiliary yarn is wrapped correctly onto the surface of the spindle tube 4, the yarn handling tool 8 is made to oscillate vertically for the length L0 of auxiliary yarn 12 to be positioned tangentially at different tube heights.

[0082] After a while without the free end 12a of the auxiliary yarn 12 wraps onto the surface of the spindle tube 4, the processing and control means supply a signal to actuate the piston and cylinder assembly 16 of the yarn retaining means to free the predetermined length L0 of auxiliary yarn 12 on outside the yarn feeding nozzle 10. Then, the robotic arm 7 is actuated to position rearwardly or forwardly the yarn feeding nozzle 10 of the handling tool 8 with respect to the auxiliary yarn 12 for a second predetermined length of auxiliary yarn to be on outside the yarn feeding nozzle 10. A new signal is supplied to actuate the piston and cylinder assembly 16 of the yarn retaining means "R" to retain this time in place the second predetermined length of auxiliary yarn 12 on outside the yarn feeding nozzle 10.

[0083] It has been found that the length L0 of the auxiliary yarn 12 to be retained outside the yarn feeding nozzle 10 may vary depending mainly on the friction coefficient of the surface onto which the yarn is to be wrapped. For example, a longer length L0 of auxiliary yarn 12 may be necessary for aiding wrapping yarn if the surface of the spindle tube 4 is empty of yarn, whereas a shortest length L0 is necessary if the surface onto which the free end 12a is to be wrapped has yarn package "P".

[0084] Wrapping of the free end 12a of auxiliary yarn 12 triggers stopping rotation of the spindle tube 4 and activation of the air suctioning means to suction air inside the yarn feeding nozzle 10. For the illustrated embodiment, the suctioning of air is carried out by injecting air into the first Venturi tube 13 and air injector assembly. Nevertheless, other well-known air suctioning means may be envisaged for suctioning air into the yarn feeding nozzle 10.

[0085] Figure 7 shows a perspective view of the yarn handling tool 8 attached to the robotic arm 7, and the robotic arm 7 carrying out a precise and particular motion to cause the gripping element 11 to hold or grasp the auxiliary yarn 12 on outside the yarn feeding nozzle 10 to form the threading section"S" (see, figure 8).

[0086] In the claimed system and method, the air suctioned inside the yarn feeding nozzle 10 (see, arrows) keeps the auxiliary yarn 12 at an appropriate tension and allows the yarn handling tool 8 to displace relative to the auxiliary yarn 12 for the gripping element 11 to hold or grasps the auxiliary yarn 12 on outside the yarn feeding nozzle 10.

[0087] In contrast to the known methods, the claimed method allows the threading and piecing operations to be carried out with only one yarn handling tool 8 attachable to a robotic arm 7. The processing and control means of the system are configured to provide a motion signal to the robotic arm 7 to position the threading section "S" at the flange 3 of the ring 1 for the threading section "S" to be threaded into the ring traveller 2 (see, figure 9).

[0088] As it is shown in figure 9, an air conduct 21 is arranged on the yarn handling tool 8 for propelling air (see, arrows) to the ring 1 to cause deliberate motion of the ring traveller 2 on the flange 3 of the ring 1 during the threading operation.

[0089] Once the auxiliary yarn is threaded into the ring traveller 2, the robotic arm 7 displaces and positions the yarn handling tool 8 for threading the auxiliary yarn 12 into the balloon constriction ring 5 (see figure 10). Then, the robotic arm 7 positions the yarn handling tool 8 so that the auxiliary yarn 12 on outside the yarn feeding nozzle 10 is pieced with the roving issuing the front drafting rollers 6 (see, figure 11). All these operations take place without the spindle tube 4 rotating to obtain maximum preciseness.

[0090] In a final step of the method, the robotic arm 7 positions the yarn handling tool 8 at a predetermined distance from a cutting tool (not represented) for said cutting tool cuts the auxiliary yarn 12 at a position configured to obtain anew the predetermined length L0 of auxiliary yarn 12 on outside the yarn feeding nozzle 10. The system is then ready for starting a new piecing cycle at a new spinning station where breakage of yarn is detected.

[0091] As previously stated, if during handling either the gripping element 11 or the yarn feeding nozzle 10 collides accidentally with the oscillating ring rail, the end part 9a of the frame structure 9 of the yarn handling tool 8 may bend or flex to allow components to reposition in order to avoid any failure or stopping of the robotic arm 7.

[0092] Summarizing, the present invention provides a system and method for piecing a free end 12a of auxiliary yarn 12 that, in contrast to the known piecing methods, provides high reliability and preciseness of both threading and piecing operations. Besides, the claimed method significantly simplifies the piecing process since threading and piecing operations may be carried out with only one yarn handling tool 8, preferably, one yarn handling tool 8 attachable to a robotic arm 7 with at least six degree of freedom of motion.

[0093] For an unillustrated embodiment, no robotic arm is used and the yarn fastening means are arranged on a second tool of the automatic handling means. In this case, the yarn handling tool would include; a frame structure 9 attachable to the automatic handling means, an end part 9a of said frame structure 9, a yarn feeding nozzle 10 attached to the end part 9a of the frame structure 9 to supply a free end 12a of auxiliary yarn 12, air suction means 13 arranged to suction air into the yarn feeding nozzle 10, and also preferably; air blowing means 14 arranged to inject air into the yarn feeding nozzle 10 and yarn retaining means "R" configured to retain in place a predetermined length "L0" of auxiliary yarn 12 on outside the yarn feeding nozzle 10.

[0094] In this unillustrated embodiment, the yarn fastening means could be configured as a pincer or suction tube attached on the second tool to fasten the auxiliary yarn 12 on outside the yarn feeding nozzle and help the yarn handling tool 8 to carry out the threading and piecing operations.

[0095] 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 an embodiment has been disclosed where the yarn fastening means are configured as a gripping element 11 attached to the yarn handling tool 8, it would be possible to provide another embodiment where the yarn fastening means were configured as a pincer, or as a suction tube, arranged on the claimed yarn handling tool, or on a different tool, of the automatic handling means.

Examples

Embodiment Construction

[0064]Following is a description of the claimed invention with reference to drawings of figures 1 to 11 representing an exemplary embodiment of the invention applicable to a ring spinning machine, which comprises a row of spinning stations arranged next to each other and a common ring rail (not shown) mounted displaceably up and down on the frame of the machine.

[0065]At each spinning station, a ring 1 is attached to the ring rail and a ring traveller 2 is movable mounted on a flange 3 of the ring 1. A revolving spindle (not shown) is arranged in the axial vertical axis of the ring 1. On the revolving spindle is placed a spindle tube 4 on which a package "P" of yarn is formed by spinning in a well-known manner, resulting in the formation of a cop. During spinning, the ring traveller 2 and the yarn threaded therein run round the spindle tube 4 on the flange 3 of the ring 1 for the yarn is wound onto the surface of the spindle tube 4. Arranged above the revolving spindle tube 4 is a ba...

Claims

1. A yarn piecing system for piecing auxiliary yarn (12) on a spindle tube (4) at a spinning station of a ring spinning machine, comprising; - yarn supplying means for supplying a free end (12a) of auxiliary yarn (12) to the spindle tube (4) onto which said free end (12a) is to be wrapped, said yarn supplying means including a yarn feeding nozzle (10) for feeding the free end (12a) of said auxiliary yarn (12) to the spindle tube (4), - yarn fastening means (11) for fastening the auxiliary yarn (12) on outside the yarn feeding nozzle (10) to form a threading section ("S") of auxiliary yarn (12) once the free end (12a) of the auxiliary yarn (12) is wrapped onto the spindle tube (4) and, - automatic handling means (7) for handling the yarn supplying means and the yarn fastening means (11), said automatic handling means (7) include a yarn handling tool (8) where at least said yarn feeding nozzle (10) is mounted, said yarn fastening means (11) being mounted on said yarn handling tool (8) or on a different tool of said automatic handling means (7), characterized in that the system comprises; - air suction means (13) arranged to suction air into the yarn feeding nozzle (10), and - processing and control means configured to supply an activation signal to said air suction means in order to suction air into the yarn feeding nozzle (10) once the free end (12a) of the auxiliary yarn (12) is wrapped onto the spindle tube (4) and rotation of the spindle tube (4) is stopped.

2. A yarn piecing system according to claim 1, wherein the yarn handling tool (8) comprises; - a frame structure (9) configured to be attached to the automatic handling means (7), - an end part (9a) of said frame structure (9), - the yarn feeding nozzle (10) attached to the end part (9a) of the frame structure (9), - the yarn fastening means (11) attached to the end part (9a) of the frame structure (9), and - the air suction means (13).

3. A yarn piecing system according to any of claims 1 or 2, wherein said yarn supplying means comprise; - air blowing means (14) arranged to inject air into the yarn feeding nozzle (10), and - yarn retaining means ("R") configured to retain in place a predetermined length (L0) of auxiliary yarn (12) on outside the yarn feeding nozzle (10), and - wherein the processing and control means are configured to supply an activation signal to said air blowing means (14) to blow the free end (12a) of said predetermined length (L0) of auxiliary yarn (12) on outside the yarn feeding nozzle (10) while the yarn handling tool (8) approaches the revolving spindle tube (4) at the beginning of the piecing cycle.

4. A yarn piecing system according to any of claims 1 to 3, wherein said yarn fastening means comprise at least one gripping element (11) for fastening the auxiliary yarn (12) on outside the yarn feeding nozzle (10), and said gripping element (11) being arranged on the yarn handling tool (8) to allow the yarn handling tool (8) to form the threading section ("S") of auxiliary yarn (12).

5. A yarn piecing system according to claim 2 , wherein both the yarn fastening means (11) and the yarn feeding nozzle (10) are integrally attached to the end part (9a) of the frame structure (9) of the yarn handling tool (8).

6. A yarn piecing system according to claim 5, wherein the end part (9a) of the frame structure (9) is configured as a tolerance absorbing structure in order for the end part (9a) to bend or flex to absorb operating tolerances of the yarn piecing system.

7. A yarn piecing system according to any of claims 1 to 6, wherein said automatic handling means comprise the yarn handling tool (8) attached to a robotic arm (7).

8. A yarn piecing system according to claim 7, wherein said robotic arm (7) has at least six degrees of freedom of motion to allow the yarn fastening means to form the threading section ("S") of auxiliary yarn (12).

9. A yarn piecing system according to any of claims 1 to 8, wherein said air suction means comprise a first Venturi tube (13) and air injector assembly arranged to suction air into the yarn feeding nozzle (10) upon receiving an activation signal from the processing and control means.

10. A yarn piecing system according to any of claims 1 to 9, when dependent of claim 3, wherein said air blowing means comprise a second Venturi tube (14) and air injector assembly arranged to blow air into the yarn feeding nozzle (10), upon receiving an activation signal from the processing and control means.

11. A yarn piecing system according to any of claims 9 and 10, or according to claims 9 and 10, wherein the Venturi tubes (13, 14) of said first and / or said second Venturi tube and air injector assemblies are configured and arranged so that the auxiliary yarn (12) passes along the Venturi tubes (13, 14) before being supplied through the yarn feeding nozzle (10).

12. A yarn piecing system according to claims 10 and 11, when dependent of claim 3, wherein said yarn retaining means ("R") are arranged in between the first and second Venturi tubes (13,14) and air injector assemblies.

13. A yarn piecing system according to any of claims 1 to 12, when dependent of claim 3, wherein said yarn retaining means ("R") comprise; - a spring loaded slipping plate (15) to retain in place by contact against a second plate (19) the predetermined length (L0) of auxiliary yarn (12) on outside the yarn feeding nozzle (10), and - a piston and cylinder assembly (16) arranged to actuate at least a compression spring (17) against the slipping plate (15).

14. A yarn piecing system according to claim 13, where the processing and control means are configured; - to supply a signal to actuate the piston and cylinder assembly (16) of said yarn retaining means ("R") to free the predetermined length (L0) of auxiliary yarn (12) on outside the yarn feeding nozzle (10) after a predetermined time has elapsed without the free end (12a) of auxiliary yarn (12) being adhered onto the spindle tube (4), - to supply a signal to actuate the automatic handling means (7) to position rearwardly and / or forwardly the yarn feeding nozzle (10) of the handling tool (8) with respect to the auxiliary yarn (12) for a second predetermined length of auxiliary yarn (12) to be on outside the yarn feeding nozzle (10), and - to supply a signal to the piston and cylinder assembly (16) of said yarn retaining means ("R") to retain in place the second predetermined length of auxiliary yarn (12) on outside the yarn feeding nozzle (10) at the beginning of the piecing cycle.

15. A method of piecing auxiliary yarn on a spindle tube at a spinning station of a ring spinning machine comprising the steps of; a) supplying a free end (12a) of auxiliary yarn (12) by means of a yarn feeding nozzle (10) arranged on a yarn handling tool (8) of an automatic handling means (7), b) approaching the free end (12a) of auxiliary yarn to a spindle tube (4) of a revolving spindle to cause wrapping of the free end (12a) of the auxiliary yarn (12) onto the spindle tube (4), c) stopping rotation of the revolving spindle tube (4), d) after step c), suctioning air into the yarn feeding nozzle (10), and e) while suctioning air into the yarn feeding nozzle (10), positioning the yarn handling tool (8) to carry out a threading and piecing operation, wherein the threading operation includes the step of fastening auxiliary yarn (12) on outside the yarn feeding nozzle (10) by means of a yarn fastening means (11) mounted on the yarn handling tool (8) or on a different tool of said automatic handling means (7) to form a threading section ("S") of auxiliary yarn (12).

16. A method of piecing auxiliary yarn according to claim 15, wherein; - step a) comprises retaining in place a predetermined length (L0) of auxiliary yarn (12) on outside the yarn feeding nozzle (10), and - step b) comprises blowing air into the yarn feeding nozzle (10) to position the predetermined length (L0) of auxiliary yarn (12) tangentially to the spindle tube (4) for aiding wrapping.

17. A method of piecing auxiliary yarn according to claim 16, wherein step b) comprises moving in an oscillating manner the yarn handling tool (8) while blowing air into the yarn feeding nozzle (10).

18. A method of piecing auxiliary yarn according to any of claims 15 to 17, wherein the yarn fastening means comprise at least one gripping element (11) and wherein the step of fastening the auxiliary yarn (12) on outside the yarn feeding nozzle (10) to form the threading section ("S"), comprises fastening auxiliary yarn (12) by means of said at least one gripping element (11) integrally attached to the yarn handling tool (8).

Images