GB2178069A - Open-end yarn piecer - Google Patents

Abstract

Methods and Apparatus for piecing a rotor spinning machine having a plurality of spinning stations, each of which includes a rotor unit (10) package forming means (14) to form a package of yarn produced at the unit, a nip roll pair (12) for withdrawing yarn from the unit and feeding it to said package forming means (14), feed means (30) selectively operable to feed fibers to said unit for spinning into yarn and drive means operable to drive the rotor unit (10) at a selected operating speed and to drive the package forming means, nip roll pair and feed means at respective speeds each in a selected relationship to said operating speed. Withdrawal of yarn (18) after piecing with a fiber ring in the rotor is effected by re-engaging previously separated withdrawal rolls on the rotor spinning machine. Feeding of the seed yarn back to the rotor and initiation of withdrawal of the seed yarn and newly spun yarn pieced thereto can be effected while the spinning unit is operating at a predetermined constant speed, preferably at or near the selected normal operating speed for the spinning unit. A predetermined time period is defined at the expiry of which withdrawal of seed yarn is commenced. By adjusting the backfeed of seed yarn relative to the predetermined time period, the duration of a "rest-period" is determined. During this rest period, the end of the seed yarn is in the rotor groove and twist is transferred from the seed yarn to fibers in the groove. By control of the rest period, twist transference to the fibers is controlled. <IMAGE>

Description

SPECIFICATION Open-end yarn piecer The present invention relates to methods and appar atus for piecing a rotorspinning machineofthetype (hereinafter referred to as "type described") comprising a plurality of spinning stations, each including a rotor unit, package forming means to form a package of yarn produced at the unit, a nip roll pairforwithdrawing yarn fromthe unitandfeeding into said package forming means, feed means selectively op erabletofeed fibersto said unitforspinning into yarn and drive means operable to drive the rotor unit at a selected operating speed and to drive the package forming means, nip roll pairandfeed means at respective speeds each in a selected relationship to said operating speed.

Rotor spinning machines ofthe type described are now extremely well-known in the rotor spinning art.

By way of example only, details of such machines can be obtained from United States Patent Specification No.3375649.

At present, the majority ofthe rotor spinning machines in commercial use are operated by manual attendance.

In particular, start-up of the machine, doffing of packages and repair of thread breaks are dealt with by hand. In each of these operations, a so called "piec ing" operation is required; that is, a previously spun "seed" yarn must be backfed into the rotor spinning unit to join or "piece" with a ring offibersformed in the rotor, the seed yarn then being withdrawn from the spinning unit and bringing with it newly spun yarn formed in the rotor.

With increasing rotor speeds, particularly speeds substantially in excess of 50'000 RPM, manual piecing becomes increasingly difficult. Since commercial rotor speeds are now approaching the 80 to 90'000 RPM region, it is becoming imperative to provide at least mechanised piecing assistance and preferably fully mechanised, or automated, machine attendance.

A commercial rotor spinning machine comprises a large number (usually approx. 200) spinning stations.

For economic reasons, it is preferred not to provide individual piecing means at each ofthese stations, but instead to provide a travelling piecing apparatus movable from station to station and capable of performing a piecing operation atanyselected station.

One example of a travelling piecing apparatus of a kind referred to above is shown in United States Patent Specification No.4041684. Said specification shows a piecing apparatus with a meansforseparating the nip roll pairon a station to be serviced and for threading a seed yarn (a broken yarn end on the yarn package at the station) with the separated nip rolls before backfeeding the seed yarn into the spinning unit.

Subsequent withdrawal of the seed yarn and newly formed yarn pieced thereto is effected by re-engaging the nip roll pair. However, so far as present applicants are aware, the company owning US-Patent 4041684 has not produced a commercial apparatus in accord ancewiththe patent. Instead, the system offered by that company on the market involves withdrawal of seed yarn and newlyspunyarnfromthe rotorspinning unit viva a withdrawal path passing through the piecing apparatus and by means of a withdrawal unit specifically provided for this purpose in thetravelling piecing apparatus. All ofthe commercially available systems known to the present applicatns also involve use of a special yarn withdrawal uniton the travelling piecing apparatus.After completion ofthe yarn piecing operation, therefore, control of the withdrawal operation has to be passed back from the piecing apparatusto the machine -this substantially compli- cates operation of both the travelling piecing apparatus and the machine.

Furthermore, several commercial piecing systems presently available depend upon piecing at a rotor speed which is substantially lower than the normal operating speed of the rotor, e.g. a piecing speed of approx. 40'000 RPM in comparison with a normal operating speed in the region 70 to 80'000 RPM. By way of example only, details of a "low speed piecing" technique can be seen from US Patent Specification 4012116. The lowspeed piecing technique renders certain factors less critical to the success of the piecing operating. However, it also brings certain complications which will be explained in detail below in the course of explanation of the illustrated embodiments of the present invention and by way of contrastwith the relatively straightforward technique enabled by this invention.

Present Invention In the present invention, withdrawal ofyarn after piecing with a fiber ring in the rotor is effected by re-engaging previously separated withdrawal rolls on the rotor spinning machine, as is known from the US Patent referred to above. Feeding of the seed yarn back to the rotor and initiation of withdrawal ofthe seed yarn and newly spun yarn pieced thereto can be effected while the spinning unit is operating at a predetermined constant speed, preferably at or nearthe selected normal operating speedforthespinning unit. Thus, if the machine is set to drive its spinning units at, say, 80'000 RPM, the piecing operation is preferably carried out while the spinning unit is operating ator nearto 80'000 RPM.

A predetermined time period is defined at the ex piry ofwhich withdrawal of seed yarn is commenced.

By adjusting the backfeed of seed yarn relative to said predetermined time period, the duration of a "rest period" is determined. During this rest period, the end ofthe seed yarn is in the rotor groove and twist is transferred from the seed yarn to fibers in the groove.

By control of the rest period, twist transference to the fibers is controlled.

Further features ofthe invention will be apparent from the description of the drawings, in which Figure lisa diagrammatic side elevation of one spinning station of a rotor spinning machine ofthe type described, the diagram showing the relations of the parts of the station and co-operation thereof with a travelling yarn piecer, Figure2 is a speed vstimediagram for use in explanation ofthe piecing technique ofthe invention, the speed scale (vertical axis) being differentforthe rotor speed and yarn speed diagrams.

Figure 3 is a more detailed side elevation, also diagrammatic, of the package forming means of a spinning station and co-operation thereof with the piecer, the spinning station being on the opposite machine side relative to that shown in Figure 1, Figure 4 is a view in the direction of arrow A in Figure3 and Figure 4A is a detail of part of Figure 4, FigureS is a diagrammatic side elevation ofthe path of movement of a yarn threading element of a piecer according to the invention and Figure 5A is a detail of part of Figure 5, Figures 6-9 inclusive are diagrammatic side elevations of successive yarn paths adopted by a seed yarn during preliminary stages of a piecing operation according to the invention, Figure 10is a diagrammatic representation of a yarn reserve release device for a piecer according to the invention, Figure 11 is a diagrammatic representation of a nip roll pairofa machine ofthe type described and cooperation thereof with roll separating means for a piecer according to the invention, Figure 12 is a block diagram of a timing means fora piecer according to the invention, Figure 13 is a plan view of the floor portion of a rotorshowing an arrangementof markings adapting the rotorfor use with the piecer of Figure land Figure 14 is a diagrammatic representation of a yarn clamping device suitable for use in a piecer according to the invention.

In the description of the drawings and in the claims the terms "upstream" and "downstream" are used.

These terms relate directions and positions to the direction of travel oftheyarn out of the spinning unit to the packageforming means during normal spinning operation, that is, in Figure 1 "downstream" is upwards relative to the Figure since the package forming means is located above the spinning unit.

Description ofthe drawings The principles involved in the present invention will first be described with reference to Figures 1 and 2.

Mechanismsfor putting those principles into effect will then be described with reference to the other drawings. Figures 1 and 2 are diagrammatic only and are in now way intended to represent exactly either a practical machine design or an exact piecing sequence.

Thefull line diagram in Figure 1 illustrates in side elevation onespinning station of an open-end spinning machine. There wouid be many such stations arranged side by side in a practical machine, nowadays commonly up to 100 stations per machine side.

The dotted line illustration in Figure 1 represents a piecing apparatus which normally travels to and fro past the spinning statins but which can be stopped in alignment with a selected station in order to perform a piecing operation as will be outlined. The dotted line illustrations in Figure 1 also show certain modified positions ofthe elements ofthe spinning station and ofthethread path during a piecing operation.

The illustrated spinning station comprises a spinning unit indicated generally by the numeral 10, a yarn withdrawing means indicated generally by the numeral 12 and a package forming means indicated generally by the numeral 14. In normal operation of the spinning station, a sliver 16 of staple fiber is drawn into the unit and is converted therein to a yarn 18. The yarn is withdrawn from unit 10 by means of the withdrawal means 12 and is forwarded to the package forming means 14 at which it is wound into a package 20.

The spinning unit lOis ofa typeverywell known in therotorspinning art. Detailscan beomitted.The general type of spinning unit involved can be seen from US Patent Specifications 3511045 and 4009562.

Figure 1 shows the outline of a unit housing 22 which is pivotally mounted on a tube 24 which extends over thefull length ofone machine side being fixed inthe machine frame and common to all spinning stations on the one machine side. Extending through the bore oftube 24 is a worm gear 26 also extending along a complete machine side.

At each spinning station there is a drive shaft cou pling (not shown) to the worm gear 26 which therefore drives the input side of a clutch 28. The output side of clutch 28 is coupled to a knurled feed roller 30.

Feed roller 30 draws the sliver 16 into the spinning unit and presents the sliverto an opening roller32 having pins or teeth to comb individual fibers out of the presented sliver end. The fibers extracted from thesliverareforwarded by an airstream to a rotor 34.

Opening roller 32 is driven by a whorl 36 projecting from the underside of the housing 22 so as to be engageable with a drive belt (not shown) common to all ofthe spinning stations.

Rotor34 is carried by way of a bearing unit38 on a carrier40 which is pivotally connected to the housing 22. Figure 1 shows the parts in their normal operating disposition in which housing 22 is latched in an "upright" disposition and carrier 40 holds the axis of rotor 34substantially horizontal. Housing 22 can be unlatched and tilted forwardly (that is, in an anticlockwise direction) on its pivot mounting on tube 24 and carrier 40 can simultaneously pivot rearwardly (in a clockwise direction) on its pivotal connection with housing 22. In this manner, the rotor unit (34,38,40) can be separated from the fibre feed system (30,32) for ready access to the interior of the rotor.

The air stream which draws fibers from the opening roller 32 to the rotor 34 is created by a vacuum applied to the housing 22forexample as indicated at42.A feed and guidetube (not shown) leadsthefibercarrying air stream from the opening roll through a rotor cover (not shown) into the rotor interior where the fibers are separated from the carrying air by centrifugal force and are laid as a fiber ring in the so called "rotor groove" at the maximum interiordiameter of the rotor. The air escapes over the rotor rim and is removed by the suction system (not shown).

Forfurther detail of these arrangements see US Patent 3481129.

The formed yarn is withdrawn from the rotor via a withdrawal tube 44 which extends at its upstream end through a withdrawal nozzle 46 mounted in the rotor cover. After leaving the withdrawal tube 44, the yarn passes a pivotable monitor 48. This monitor is also of a well known type comprising a lever pivoted to swing on an are which intersects the normal yarn path. The lever is biased towards one position on its arc and is maintained speced from that position by the normally running yarn. lftheyarn breaks, orthe yarn tension drops severely, the lever is pivoted under its bias to close a switch indicating a fault condition. Such a monitor is shown, for example, in US Patent No. 3404524.

From monitor 48, the yarn passes to the withdrawal means 12 which comprises a guide 50, a drive roller 52 and a pressure roll 54. Guide 50 reciprocates the yarn over a slig httraverse axially of the withdrawal rollers 52, 54to avoid presistentwearatone location ofthose rollers. The primarywithdrawalfunction is performed atthe nip normally formed between the rollers 52 and 54. Roller 52 extends along the complete side ofthe machine, being common to all stations. It is driven in a clockwise direction about its own axis, as indicated by the arrow in Figure 1. At each spinning station there is a respective pressure roller 54 mounted by a carrier arm on a rod 56 extend ingthefull length ofthe machine side.The carrier arm is pivotable on the rod 56to move the roller54from thefull line position tothe dotted line position. During normal operation, the roller 54 is in its full line position in which it engages roller 52 to form a nip there between. The yarn 18 is withdrawn from the spinning unit by means of this nip and the drive on the roller 52.

The withdrawal speed is determined by the speed of rotation ofthe roller 52.

The package forming means 14 comprises a fixed guide 58, a traversable guide60 and a drive roller62.

Guide 60 is traversed (by means not shown) axially of the package 20. The latter normally rests in frictional engagement with the roller 62 which extends along a full machine side and is common to all spinning stations. Roller 62 is driven to rotate clockwise as viewed in Figure 1 about its own longitudinal axis, thereby rotating the package in an anti-clockwise direction.

The traverse motion ofthe guide 60 enablesformation of a cross-wound package. The portion of guide 58 which contacts the yarn is formed to even outyarn length variation which would otherwise occur during the traverse motion. This general arrangement is also very well known in the art.

Package 20 isformed on a bobbin tube 64carried between a pair of arms of a package cradle. Only one arm 66 can be seen in Figure 1.The arms are pivotable together about a pivot mounting 68 on the machine frame, partofwhich is shown at 70.

In the event of athread-breakwhich may be due to a fault or may be deliberately induced (for example at completion of winding of a package of a predeter minedsizeorwhencleaningofthespinning unit lOis due),thethread breaksignal issued by the monitor48 causes operation of a mechanism (not shown) to lift the package 20to the position illustrated in dotted lines in which it is clear of roller 62. The lattercontinues in rotation to drive the packages at the other spinning stations, but rotation ofthe package ceases at the station with the broken thread. The thread break signal also opens the clutch 28, so that feed of sliver 16 also ceases. The drive to the gear 26, wheel 36, rotor 34, withdrawal roll 52, and traverse guide 60 continues.

A call signal is also issued to cause the automatic piecer 72 to stop in alignment with the illustrated station. When it is correctly registered with the station, piecer 72 carried out a piecing operation which basicallyinvolvesfindingthe brokenthread end on the package 20 and feeding it back down the withdrawal tu be 44 to rejoin that end with a newly formed ring of fibers in the rotorgroove.As soon as the backfed yarn has formed an effective join with the fiber ring in a rotor, withdrawal of the newly formed yarn must be restarted.As is well known in the art, and widely documented in the relevant literature over the last ten years, control ofthethree operations (yarn backfeed, fi ber feed and yarn withdrawal) is critical and extremely difficultto achieve at least with rotor speeds substantially higherthan 50'000 RPM.

Accordingly, in all currently available automatic piecing devices, steps have been taken to modify the normal spinning conditions for the purposes ofthe piecing operation. For example, in all commercially available piecing devices, the yarn path between the spinning unit and the package is diverted to pass through the piecing device, and the yarn must be passed backto the machine atthe completion of a successful piecing operation. In certain systems, piecing is effected at a rotor speed which is lowerthan the normal operating speed, usually during acceleration of the rotortowards its normal operating speed.

Despite these measures, the piecings, or joins, obtained from the currently available devices do not always meet the requirements of the further processing industries, and the piecing is frequently cut out and replaced by a knot or a splice after spinning atthe spinning unit has been successfully restarted.

All of the above steps complicate the system and make it more expensive. In the system now to be described, piecing is effected under conditions approaching as closely as possible to those which occur during the normal spinning operation, The dotted lines extending between the piecing device 72 in Figure 1 and the spinning station in that Figure indicate the main points at which the piecing device intervenes in the spinning station to effect piecing. Thus, the piecer takes over control of the position ofthe package 20 relative to the friction roller 62 as indicated by line 74joining the piecerto package holder arm 66. The piecer can be provided with a suitable leverforthis purpose.The piecer also lifts pressure roller 54 away from drive roller 52 and moves it to the dotted line position as indicated bythe line 76 joining the piecertothat position. Again, the piecer can be provided with a suitable leverforthis purpose.

The piecerfurtherforms a yarn reserve which is a defined length of yarn, the length ofthe reserve being equal to the distance through which the yarn end will move in the last stage of the piecing operation in order to bring it into contact with the fiber ring in the rotor groove. For this purpose, the piecer locates a reserve forming device 78 adjacent the exit end ofthe withdrawal tube 44.

The piecer may have a device for sensing the speed of rotation ofthe rotor. The device is indicated bythe dotted line 80 in Figure 1 and a suitable arrangement will be described below. The piecer also has a means (indicated by the dotted line 82) forcontrolling opera tion oftheclutch 28.

The piecer 72 is also provided with certain elements which have not been shown in Figure 1. In particular, there is a meansforfindingthe broken thread end on the package 20 and a deviceforthreading end on the package 20 and a deviceforthreading thefoundyarn along the thread path indicated by dotted line between package 20 and the exit end ofthe withdrawal tube 44. Itwill be noted, in particular,thattheyarn is threaded between the separated nip rollers 52,54 and into the reserve forming device 78.There is also a device which forms a prepared end on the yarn and a device for performing a preliminary backfeed operation in which this prepared yarn end is inserted into the downstream end ofthe withdrawal tube 44 and is drawn by the suction on thattube to a position ator nearthe upstream end of the nozzle 46. Thus, the final backfeed phase which is performed underthecontrol ofthe reserve device 78, carries this yarn end from the nozzle 46 into the rotor groove.

The piecerfurther includes a rotor cleaning device.

The device will not be described in the present application but can be formed, for example, in accordance with our Swiss Patent Application No.3631/82. Cleaning ofthe rotor is performed simultaneouslywith the end seeking operation. In order to perform the cleaning operation, the spinning unit must be opened in orderto provide access to the rotor interior, and the rotor must be baked to a standstill.The dotted line yarn path shown in Figure 1 and the location ofthe yarn end within the nozzle 46 are established after reclosingofthespinning unitfollowing completion of the cleaning operation. At that time, also, drive will be reestablished with the rotor, which will begin to accel eratetowards its normal operating speed.

Piece 72 also includes a control means 84 which controls all functions ofthe piecer according to a predetermined sequencing program. Certain aspects of the program will be described in further detail with reference to the more detailed mechanisms. However, particular attention will first be paid to the final stage ofthe piecing operation, in which a) a ring offibers of controlled dimensions is formed in the rotor groove by operation of clutch 28, b) the prepared yarn end is fed back from the nozzle 46 to join with this fiber ring by operation ofthe reserve device 78, and c) withdrawal of newly formed yarn is restarted by return of roller 54 into re-engagement with roller 52to formthewithdrawal nip.

The timing ofthe commencement offiberfeed in relation to the other operations has been extensively dealt with in the literature and will not be covered again here. Reference can be made for example to US Patent Specification 4102116. Briefly, the aim of fibber feed control is to achieve ring of appropriate dimensions so that the piecing is neithertoo thick nortoo thin in relation to the normal yarn count. In general, this is a matter of timing ofthe operation of clutch 28 in relation to the othertwo operations which will be discussed in additional detail with reference to Figure 2.

In the graph of Figure 2 the vertical axis represents speed and the horizontal axis representstime. The line R represents the speed ofthe rotor, and the line Y represents the speed ofthe yarn end/piecing. The scale of the diagram is different for the rotor speed and the yarn speed, since onlythe principle is of importance and absolute speed values are irrelevant.

At the left hand side ofthe diagram of Figure 2 the rotor is assumed to be reconnected with its drive after the cleaning operation. The rotor speed then follows an acceleration curve which will be dependent upon the overall design ofthis system and which will be inevitablysubjecttominorvariationsfrom one station to another because of manufacturing and assemblytolerances. After the rotor has reached its normal operating speed N, the control 84 provides a start signal to start the final piecing stage. The issuance of the start signal is dependent upon the completion of the preliminary piecing operations referred to above which will normally last longerthan the acceleration time ofthe rotor R.

The control 84 now defines a predetermined time T during which theformation ofthefiberring,theback- feed oftheyarn end and joining oftheyarntothefiber ring can occur. At the expiry of this time T,the roller 54 has again engaged the roller 52 so that withdrawal of yarn from the spinning unit is commenced.

In accordance with the backfeed operation indicated bythefull lineYshown in Figure 2, backfeed is assumed to be initiated as soon as the start signal is issued. As indicated by the dotted line, there can be a delay between the start signal and initiation of backfeed. Device 78 is operated to provide a controlled backfeed such that the yarn is continuallytensioned along its length during the backfeed operations and so thatthe yarn end arrives in the groove with a slight time advance relative to the start of yarn withdrawal.

Forthe backfeed operation indicated by full line in Figure 2, the corresponding time advance is indicated att. The time advance may be greater or less depending upon delay in initiation ofthe backfeed.

Consider nowthe motion oftheyarn end between the upstream end of nozzle 46 and the rotor groove.

As the yarn end enters the rotor system, the yarn begins to rotate about the nozzle axis with the rotor andtheyarn end is drawn out by centrifugalforce towards the rotor groove. Rolling of the yarn around the internal surface of the nozzle 46 increases the already available twist in the yarn. When the yarn end reaches the groove and begins to mix with the fibers therein, the yarn twist begins to collect the fibers from the groove and joins them intotheyarn.

In order to form a good join between the backfed yarn end and the fibers, a predetermined quantity of twist must be transferred from the backfed yarn to the newly forming yarn in the rotor groove. If the degree of twist transference is too low, the strength of the join will be inadequate andtheyarn will breakwhen withdrawal is attempted. If an attempt is madeto transfer too much twist to the piecing, then a yarn breakwill occur due to "overtwist" eitherofthe back- fed yard or of the piecing. The degree oftwisttrans- ference to the piecing is dependent upon two factors, namely a) the amount of twist present in the backfed yarn when it arrives in the rotor groove, and b) further twist imparted to the backfed yarn while the yarn end is present in the rotor groove and form ingthejoin.

Factor a) is dependent upon the backfeed speed in relation to the rotor speed and factor b) is dependent upon the length of the advance referred to above,that is the duration ofthe "rest" period during which the yarn end remains in the groove waiting for yarn withdrawal to begin. In principle, the degree oftwisttrans ference can be controlled by controlling both factors a) and b) above, but we preferto apply the main control via factor b) (that is by adjustment of the rest period) and to hold factor a) constant (that is to maintain constant backfeed speed for all piecing operations). Also, in principle, it would be possible to detect the completion of the backfeed movement and then to measure out a defined rest period.However,the rest period required in practice is of extremely small duration (up to 10 millisecs) and it is impractical to initiate the mechanical operations involved in yarn withdrawal within thevery shorttime availableafter sensing of completion of the backfeed movement.

For the above reasons, it is preferred to define the initiation ofwithdrawal by reference to the start signal and to define the duration ofthe rest period by reference to the delay (or lack of it) between the start signal and the initiation of the backfeed movement.

The required duration of the rest period will depend upon the operating circumstances, and in particular upon the rotorspeed and yarn count.Aheavieryarn count will require greatertwisttransference and thus a longer rest period.

Closing of the clutch 28 is also preferably effected by reference to the same start signal. Closing ofthe clutch must be effected at a stage of the piecing sequence such that a fiber ring of the required dimensions is available in the groove during the rest period to join with the yarn end. The actual stage of the sequence at which initiation offiberfeed must be effected will depend upon many factors including the mechanical design of the system and the yarn count. Frequently, fiberfeed must be commenced before start of the backfeed movement and the total time T must then be settableto allowfor an initial "feed delay" following the startsignal, plus the time required forthe backfeed movement plus the required rest period.

Approximately simultaneously with restart of yarn withdrawal, package 20 is returned to contact with the drive roll 62 so that packaging of yarn can be recommenced. There will be substantial differences in the rate atwhich yarn is taken up by the package immediately after the latter contacts the drive roller 62 depending upon the surface conditions ofthe package, and its size (weight). Accordingly, in order to take uptemporary excess yarn length between the nip rolls 52,54 and the package 20, a suction storage device of a known type may be brought into association with the yarn path between the nip rollers and the package.There will thus be substantial yarn tension variations between the nip rolls and the package, but these have no undesirable influences on the spinning operation because the nip rolls isolate these tension variationsfrom the spinning unit 10.

More detailed examples of machanisms enabling the piecing operation outlined above will now be described with reference to the remaining figures. In those figures, parts identical with a parts shown in Figure 1 are indicated by same reference numerals.

All figures are still diagrammatic, however.

Figures 3 and 4 shown the package forming means 14 and somefurtherdetails of its association with the piecer 72. In the side elevation of Figure 3 it can be seen that control of the positioning of the package 20 is taken overfrom the spinning machine buy a lever 86 on the piecer. Lever 86 acts on the outer end region of arm 66 and the piecer lever 86 is pivotable by a piston and cylinder unit 88 about a pivot mounting on the piecer from a starting position indicated by the dotted line 86A.

The package lift-off mechanism on the machine always lifts the package 20 through a predetermined distance H awayfromthefriction roll 62 regardlessof the size ofthe package (packages of totally different size are indicated by the full line and the dotted line circles 20 in Figure 3). The angle through which lever 86 must traverse from its starting postion 86A in order to reach the lever 66 is therefore dependent upon the size ofthe package when the threadbreak occurred.

This angularpostion ofthe arm 86 atthetime it engages the arm 66 is registered and is maintained by the piecer during the subsequent end seeking operation.

Ifthe arm 86 has to be moved slightly beyond this initial engagement position (for example, to enable release of the package lift mechanism on the machine) then the arm 86 is brought back to its initial engagement position in time for commencement of the end seeking operation. Thus, the "underside" of the package is at a designed spacing from the friction roller 62 regardless ofthe package size.

Ayarn end seeking nozzle 90 can be moved to the position indicated in full lines in Figure 3 in which a mouth piece on the nozzle is located in close association with the underside ofthe package. Suction is applied to the nozzle 90 via a flexible connection with suction 91, and a broken yarn end on the package is drawn into the nozzle. Successful finding oftheyarn is registered if necessary bya light beam emitted across the nozzle interior and interrupted by a found yarn end. If the yarn end sensor associated with the nozzle has not sensed the yarn therein after predetermined time delayfollowing initiation oftheyarn seeking operation, then the control 84terminates both the yarn seeking operation and the piecing operation and the station is accounted faulty.The station can be "marked" in a suitable manner so that service personnel can attend to the defect. The piecer can proceed to service other stations.

Assuming thattheyarn end is found, nozzle 90 is moved away from the package 20 towards the dotted line position shown in Figure 3, thereby creating a length Lofyarn which will be accessible to a thread ing device to be further described below. During the yarn seeking operation and the subsequentthreading operation, package 20 is rotated in the reverse direction by means of a roller 92 engaging the upper side of the package. Roller 92 is carried by a lever 94 pivotably mounted on the piecer 72, and an appropriate controllable drive means (not shown) is provided to rotate the roller.

Figure4showsthepackage20viewedfromthe direction ofthe piecer 72 and from above. The suction nozzle is assumed to be withdrawn from the package so that the yarn length L has been created, butthe orientation ofthis yarn length L relative to the central line C ofthe spinning station is completely uncontrolled immediately afterthe withdrawal ofthe suction nozzle. Accordingly, a yarn centering mechanism 96 is used to bring the yarn length L intothefull line disposition indicated on Figure 4.

Mechanism 96 comprises a carrier bar 98 which is reciprocable at right angles to the centre line C ofthe spinning station, Bar 98 carries a cantilever rod 100 which carries two thread guide elements 102, 104 respectively. Guide 102 has a yarn receiving slot 106 and guide 104 has a yarn receiving slot 108. Mechanism 96 is illustrated in Figure 4 in its start position immediately afterwithdrawal of nozzle 90. Comple- tion of nozzle withdrawal is indicated by suitable sensorwhich triggers movement of bar 98 to the right as viewed in Figure 4 from its starting position.The extend ofthe right ward movement of bar 98 issuffi- cientto traverse slot 106 ofthe guide 102 across the yarn length L, whereverthatyarn length may happen to be lying following the seeking operation.

As seen in Figure 4A in which the guide 102 is viewed in elevation from the direction ofthe package 20,the leading edge 110 ofthe guide 102 during this outward movement from the starting position is formed as a guide edgeto directthethread downwardly and over a lower-lip 112 into the slot 106. The otherside oftheslot 106, andthetrailing edge of the guide 102, isformed bya downwardly projecting finger 114, which projects slightly belowthe lip 112 to ensure that the thread is guided into the slot 106.

Guide 104 is formed similarlyto guide 102, butthe guide slot 108 of guide 104 leads the guide slot 106 of the guide 102 during the outward movement by a small distanced. Since the stroke of the outward movement of bar 98 is sufficient to sweep the trailing slot 106 across the yarn length L, the yarn length is located in both slots 106 and 108 on the completion of the outward stroke. The bar 98 now begins a return stroke (to the left as viewed in Figure 4) towards its starting position.This return stroke is, however, inter ruptedwhen the finger 1 of the guide 102 is located in alignmentwith a recess 116 provided in the upwardlyfacing surface ofthe guide member 58 ofthe machine. Bar 98 is now pivoted slightly about its own longitudinal axis so as to bring the tips of parts 112 and 114 into the recess 116; accordingly, as viewed longitudinallyoftheyarn length L, the slot 106 is closed by the upwardly facing surface ofguide member 58 and the yarn length L is effectively guided by this "closed" slot 106 without any risk of jamming of the yarn between the finger 114 and the surface ofthe guide member 58 or escape of the yarn between the lip 112 andthesurfaceofthe guide member58.The yarn length Lstill remains, however, in the slot 108 of the second guide 104 and because ofthe relative dispositions of the slots 106, 108 at this stage, the yarn length L intersects the centre line C at a slight angle as indicated in Figure 4.The portion of the yarn length Liying between the guides 102 and 104 is therefore accessible to the guide slot 1 18 (Fig u re 5A) ofathreading pin 120 which is moved along a th read- ing path 122 (Figure 5) such thatthe slot 118travels along the centre line C ofthe spinning station. The pin 120 rises along the rearward portion (piecer side) of its path 122 between the guide 104 and the bar 98, reaches a peak P on its path slightly thereafter and begins its downward travel by intersecting the yarn length Lathe point X.

In continuing its downward travel after taking up the yarn length, pin 120 sweeps outthe forward portion (machine side) of its illustrated path 122. In doing so, the pin 120 passes between the drive roller 52 and the raised pressure roller54,through an array of thread guides (further described below) in the reserve forming device 78, pastayarn clamp 124 and around an abrading roller 126. After passing the point X, pin 120 carries with it yarn which is being continuously delivered by the reverse rotation of package 20 refer red to above. The yarn length extending between pin 120 and package 20 is carried bythe pin along the path 122 lying on the centre line C (Figure 4).This yarn is therefore laid by the pin 120 on a yarn path Z 1 (Figure 6) contacting the roller 54, passing through the reserve forming devices 78, passing through the clamp 124, passing around the abrading roller 126 and extending to the nozzle 90. During the movement of the pin 120 around its path 122 (Figure 5), diverting means (not shown) diverts the yarn extending between the pin and the nozzle 90 so that this diverted yarn is not laid along the path Z but is continually taken up by the suction nozzle.

The details ofthe mounting and moving meansfor carrying pin 120 around its path 122 have not been shown in the drawings. Pin 122 is cantilevered from its mounting means so that slot 118 is provided adjacent its free end. The pin 120 can thus projectfreely into the spaces between rollers 52,54 and within the reserve device 78. The moving means can be a lever system operated from suitable cam plates 123 as is well known in the art of production of automaticyarn piecing devices.

Figure 6-9 inclusiveshowthe series of mutations ofthe yarn path following completion ofthethread- ing operation. In Figure 6, immediately after laying of the yarn on abrading roller 126, the pressure roll 54 is relatively widely spaced from the drive roll 52, the reserve device 78 is in a "receiving" condition and the clamp 124 is still open sothattheyarn can continueto pass to the suction nozzle. A sensing system (not shown) senses completion of one circuit of the path 122 by pin 120, whereupon reverse rotation ofthe package 20 is terminated, roller 54 is brought to a position close to but still spaced from roller 52, reserve device 78 is adjusted to its "end preparation" condition and clamp 124 is closed. This gives the yarn path Z 2 shown in Figure 7 with the yarn still extending beyond the abrading roller 126 along the dotted line portion ofthe path.

Reserve device 78 changes from its receiving to its end preparation condition by means of a rightward shift of a yarn guide 130 relative to a pairofyarn guides 128,132 so that a loop ofthread isformed betweentheguide pair 128,132.

With the yarn still on its Z 2 path, a second yarn clamp 134(Figures 7 - 9) is moved to a position immediately downstream from the rollers 52,54 and clamps the thread. For reasons which will be ex plained later, this second clamp is brought as close as possible to the rollers 52,54. Simultaneously, the abrading roller 126 is driven into rotation anticlockwise as viewed in Figure 7 and cuts the yarn leaving a tail 136 of an accurately defined length extending from the clamp 124. The portion oftheyarn not held by the clamp 124 is taken up by the suction nozzle 90. There is now an accurately defined length ofyarn between the clamp i34andthefree end ofthe tail 136.The action of abrading roller126 is such asto form a "prepared" yarn end which is particularly suitable for eventual joining with the fiber ring in the rotor. Such rollers are already well known in the art and will not be described in detail - see for example US Specification 3934394.

Clamp 124 is carried buy a lever 138 (Figure 5) which is pivotally mounted on the piecer 72. After completion ofthe yarn end preparation step, lever 138 is pivoted on its mounting to bring clamp 1 24to a position immediately above the exit opening from withdrawal tube 44 (Figure 8). During this movement of clamp 124, the relative positions of guides 128, 130 and 132 in reserve device 78 are adjusted continually to maintain the length ofthread betweentheclamps 134 and 124taut and under substantially constant or at least controlled tension. At the completion ofthis movement, the yarn lies on the path Z 3 shown in Figure 8 with a tail 136 lying within the mount of withdrawal tube 44.No attempt has been made in these Figures to represent accurately the geometry of this system required to produce the effect described.

The diagrams merely illustrate the principles involved. The geometry of movements of the guides 128,130 and 132 in orderto compensateforthe pivotal movement of the clamp 124 can be developed from the stated requirement of control oftheyarn length between the clamps 124 and 134.

Clamp 124 is now released and lever 138 is pivoted back to its previous position shown in Figure 5. Simultaneously, guide 128 is withdrawn from the yarn path, guide 130 is moved to the left relative to its position shown in Figure 8 and guide 132 is moved to the right relative to its position shown in Figure 8. The yarn is thus drawn along the withdrawal tube44 underthe effect of the suction intherotorhousing.Atthecom- pletion ofthis movement,theyarn lies on path Z4 (Figure 9, and also Figure 1) with a loop of yarn of defined length remaining between the guides 130 and 132 and the prepared yarn end lying atthe up- stream end of the withdrawal nozzle 46 (Figure 1).It remains, therefore, to release the thread reserve defined bythe guides 130 and 132 and to return pressure roll 54 into engagement with roller 52 as already described with reference to Figure 1.

The movements described with reference to Figures 3 - 9 inclusive can be controlled conveniently by a set of rotatable cam plates and levers controlled by suitable cam followers, the plates being rotated as a set.

Such systems have been commonly used in the design of automatic piecers currently available and are not believed to require detailed description here.

The movement described with reference to Figure 2 are not, however, controlled by cam plates but by triggerable mechanisms. A suitable mechanism for the reserve device 78 is shown in Figure 10.

Guide 132 is carried by a rod 138 coupled with a piston 140 in a cylinder 142. A second rod 144 projects from the other side of piston 140. Piston 144 can be latched in its illustrated position bya latch element 146 releasable by a release mechanism 148 upon receipt of a predetermined signal. Piston 140 adopts the illustrated position and is latched therein atthe completion ofthe preliminary operations, that is when the yarn is on path Z 4 shown in Figure 9 and Figure 1. Piston 140 is pressurized via air inlet 150to cylinder 142. Port 152 is vented. Upon release of the latch 146 bythe mechanism 148, piston 140 (and therefore guide 132) are urged to the right as viewed in Figure 10 at a speed which is controllable by adjust ment ofthe pressure applied at the inlet 150.Cylinder 142 is movable by the cam platesforthe preliminary piecing operations.

As shown in Figure 11, exactly the same principle is applicable in the case of the return movementofthe roller 54. As indicated diagrammatically at 154, a strong bias is normally applied by means of a suitable spring acting between the carrier rod 56 (see also Figure 1 )for roller 54 and the cantilever arm 156 which carries the roller at its free end. This bias urges roller 54 towards its nip position with roller 52. The free end of arm 156 is also provided with an abutment surface 158 which is engaged in the " ready" condition of Figure 9 by a latch 160 having an associated release mechanism 162 responsive to a release signal which, as will be described, is related to the start signal referred to above in description of Figure 2.The rotatable cam which moves roller 54 away from roi ler 52to its threading position (Figure 6) and back to its ready position (Figure7 and Figure 11) also acts via a lever 159 (dotted lines Figure 11) upon the surface 158, but the lever is arranged to move away from that surface when the arm 156 reaches its ready position (Figure 11). The latch 160 retains the arm 156 in the ready position, however, until the release signal is received.

Figure 12 shows a partofthe control 84designed for producing the release signals. The Figure is in the form of a block diagram, block PC representing a programmable controller. When the programmable controller has received signals on inputs (indicated generally but without reference numerals) showing that the piecer is in the ready condition, controller PC sends an output to clockCLwhich then provides output pulses at a predetermined rate to each of counters CF, CB and CW. Each ofthese counters is individually settable to provide a respective output signal when it reaches its respective set count. The output signal from counter CF is fed to a mechanism operating clutch 28 to cause operation of feed roller 30 and feed of fibers into the rotor. The output of counter CB is fed to the release mechanism 148 to release the yarn reserve device 78 and the output of counter CW is fed to the release mechanism 162to releasethe roll carrier arm 156.

Itwill I be real ised from the above that the timing means constituted by the clock and counters in Figure 12 does notdetermine alonethe periodTshown in Figure 2. That period is dependent also on the mechanical performance particularly of the trigger mechan ismsandthe bearing bywhich arm 156 is mounted upon rod 56. There is only one reserve mechanism (78) associated with the piecer 72 and its performance can be made reproduceable and can be maintained by adequate maintenance and periodic checks.

However, there is one pressure roll 54 and carrier arm 156foreach individual spinning station, and a certain amountofvariation in the performance of these units must be anticipated. There will therefore inevitably be at least some minor variation in the period Tfrom position to position, but by careful attention to the bearing mechanism, the variability can be maintained within tolerable limits.

As described above with reference to Figure 2, backfeed oftheyarn is completed before withdrawal ofnewlyspunyarn is begun. Itis importantthata controlled length of backfed yarn should penetrate into or overlap with the fibers in the rotor groove in order to ensure adequate twist transference from the yarn to those fibers. It is thus important to provide a carefully controlled length of yarn from the clamp 134 (Figure 9) tothe prepared yarn end. Furthermore,the location of clamp 134 as close as possible to, but downstream from,the nip rolls 52,54 helps to mini mite this defined yarn length.This in turn assists in reducing variability which might be introduced due to variable stretchability of different yarn types. Some stretching of the yarn must be anticipated. The effect ofthe centrifugal force during the final stage ofthe piecing operation (and hence for a given yarn stretchability, the absolute degree of stretching ofthe backfed yarn) will be lessforayarn clamped immediately downstream of the n ip rolls than for a ya rn which is permited to extend freely back to the package 20.

Clamp 134 cannot, however, be located upstream from the nip rolls 52,54 because there intends to interfere with exact performance of the final piecing stage as described with reference to Figure 2, and such interference is highly undesirable.

Clamp 134is released automatically by linkage (not shown) to the return movement ofthe nip roll to forward yarn to the package 20. As already described with reference to Figure 1, package 20 issimul- taneously returned to the friction roll 52. The tempor ary yarn store described above with reference to Figure 1 can be operated by the set of rotatable cam plates also referred to above. Although not shown in the drawings, the store can be brought against the yarn path Z 4 downstream from the clamp 134. Suitable temporary stores, preferably in the form of a suction tube with an open end immediately adjacent the yarn path are already well known in the art, see for example US Specification 4223518.

Furtherdevices, not already described above, can also be incorporated in the piecer or operated by it.

For example, ayarn qualitytestercan be mounted on the piecer so has to be brought against the yarn path by the cam plates referred to above to test the quality of a piecing. If the quality detected is unacceptable, the programmable controller PC can be arranged to induce a thread break so that the piecing operation is repeated. The system can be programmed to provide a predetermined number of repeats, and if quality is still unacceptable, the spinning station can be marked as defective and the piecer can terminate its piecing attempts, moving on to service another station. It is common practice to associate a yarn lubri cating device with the pressure roll mounting 156.

The piecer can be provided with a suitable leverto move this waxing device out of the operating range of the piecing system. Similarly, ifa spinning station includes yarn tension compensation means (for ex ample, as commonly provided where conical pack ages are to be formed), the piecer can also be adapted totemporarily move aside the tension compensator to avoid its interfering with the piecing operation.

A rotor speed sensing system may be used to check rotor speed. The system can be of a known type with a lighttransmitting tube passing through the rotor housing and permitting the piecer 72 to send a light beam through the tube to be reflected from a rotating surface, and to receive a reflected light beam. The rotating surface is provided with suitable markings modulating the reflected beam, and the piecer 72 is provided with a receiver sensitive to the modulated beam. Such a system is shown,forexample, in the DE specification (Offenlegungschrift) 2610575.

In the systems currently used it is normal practice to apply the relevant markings to a part rotating in synchronism with the rotor rather than to the rotor itself. This is not very convenient for a so called "direct bearing" rotor where the rotor itself is generally the only part readily accessible. A convenient location to provide the required markings on the rotor itself is on the rotor "floor" facing the open end ofthe rotor and spaced radially inwardly from the rotor groove. In Figure 13, for example, 164 represents the rotor rim, isthe floor ofthe rotorvisiblethrough the open rotor side, 168 is a hub by means ofwhich the rotor is connected to its drive shaft and 170 isan annularringofmarkingssuitableforusingthespeed sensing system referred to above.As illustrated, the ring 170 is divided into 8 equiangularsegmentswhich are alternately light-reflecting and non-lightreflecting. The contrast is conveniently produced by first treating the floor 166 of the rotor to provide it with a reflective surface, for example, by fine polishing and/or application of a suitable coating. The non-reflective portions are then produced by selec tively etching our eroding the surfaceto destroy its light reflecting properties preferably by converting it to a light diffusing surface. Such marking gives good contrast and an unambiguous speed signal without being detrimentai to the technology ofthe spinning operation.

The principles which have been outlined above are based upon recognition ofthe fact that currently available piecing systems have experienced difficulty in achieving close control ofthe piecing operation, particularly in its final phase. Without close control of this phase, it is impossible to obtain a piecing reliably at rotor speeds in excess of40 - 50'000 RPM. In order to improve the success rate, the current systems have altered the background conditions in one way or another. Such alteration of the background conditions inevitably introduces complication and expense, but in many instances it also makes the required degree of control overthefinal piecing phase even more difficultto achieve.For example, in a "low speed piecing" system in which yarn withdrawal is triggered at a speed below normal and on the acceleration curve of the rotor, additional variability is intro duced due to variability ofthe rotor acceleration curve from spinning station to spinning station. The piecing operation should place a controlled quantity of twist in the piecing, and sincethetwist level is directly related to the rotor speed, uncontrollable variation ofthe rotor speed during the piecing operation makes the desired control virtually impossible.

Furthermore, low speed piecing (whether it is effected on the rotor acceleration curve or at a predetermined constant speed which is lowerthan the normal operating speed) introduces complication in matching the fiber feed and the withdrawal speed to the rotor speed as the rotor accelerates from its piecing speed to its normal operating speed aftersuccessful piecing operation. The failure ofsuch matching results in production of a substantial length of yarn having a totally different characterfrom the yarn produced at normal rotor speed. The matching process necessitates, however, direct intervention of the piecer in control ofthe relevant spinning station to control its operating characteristics during the acceleration phase.Furthermore, it is extremely difficult to match the withdrawal speed to the increasing rotor speed while using the withdrawal system ofthe spinning station itself; forthis reason the currently available systems all use an initial withdrawal path passing through a substitute withdrawal system in the piecer.

The disadvantage ofthis arrangement is, however, that the yarn must subsequently be returned from the piecer withdrawal system to the spinning station withdrawal system, which introduces further problems.

Anotherapproachwhich has been adopted isto abandonattemptsto producea carefullycontrolled piecing and to attemptmerelyto obtain a piecing which enables extraction of newly formed yarn from the spinning unit. The piecing itself can then be cut outoftheyarn beforewinding up thereof on the package. The piecing is replaced by a knot or a splic ing,theyarn beingtemporarilystoredtoenablethis operation and the timig of the knotting/splicing operation therefore being less critical. The addition of the knotter/splicer clearly complicates the piecer construction and makes it more expensive.

In contrast, the principles described with reference to Figure 2 enable as manyfeatures as possible to be held constant, reducing variability in the piecing process. The rotor speed is held constant during the piecing operation, preferably at the normal operating speed so that no subsequent matching offeed and withdrawal speeds has to be effected during a rotor acceleration phase. The performance ofthe backfeed system is also held constant. The length of yarn backfed can also be held constant despite variation in the rotor diameter. The prepared yarn end should not penetrate the rotor space, that is it should not leave the withdrawal nozzle before the start of the final piecing phase.The yarn end can, however, be withdrawn from the nozzle end by a suitable amount when a rotorofsmallerdiameterthan the maximum designed rotor diameter is in use. Maintenance of these constant conditions enables the piecer to obtain close control over the final piecing phase and also enables the piecer to use the withdrawal system ofthe spinning station, despite minorvariabilityfrom station to station.

The system is not limited to details ofthe mechanisms shown in the Figures, Nor is it limited to dealing with piecing of a broken end which has wound up on a package. Upon starting up of a machine, orafterdoffing of a full package, it may be necessaryforthe piecer to restart the spinning operation when there is notyarn already available at the spinning station itself. Forthis purpose, the piecer can carry an auxiliary yarn package (171, Figure 4) from which yarn can be drawn for insertion into the spinning unitto piece with a fiber ring formed in the rotor ofthe unit.The auxiliary yarn can then be transferred to a bobbin tube inserted in the package cradle ofthe spinning station, and the auxiliary yarn can be seprated from the piecer so that furthertake-up is effected by the station. Such systems have been proposed,for exam- ple, in Swiss Specification 606533. In Figure 4, the dotted line illustration to the right ofthe main diagram shows a means for introducing the auxiliary yarntothethreading system. l72isayarnfeed means drawing yarn from the auxiliary supply.174 is a yarn manipulating means which includesayarn take-up means, for example a suction nozzle.By bringing the mouthpiece of the suction nozzle close to the feed means 172, the suction nozzle can be madeto take-upyarn from the feed means. Then, by drawing the suction nozzle away from the feed means 172 to the position shown, an accessible length ofthread 176 (chain-dotted line) is produced. The stroke of the bar 98 of centering mechanism 96 is made long enough to sweep guides 102,104 across thisthread length 176.

On its return stroke, mechanism 96 draws the au xiliaryyarn into the "threading position" aireadydescribed in relation to a broken end and indicated at L in Figure 4. Suction is simultaneously applied to nozzle 90 at a level sufficientto draw a loop of auxiliary yarn (indicated in dotted lines at 176A) into the nozzle between forwarding means 172 and guide 104.

Threading ofauxiliaryyarn into the piecing system is identical to threading of a broken end; however, a knife (not shown) in forwarding means 172 is oper ated simultaneouslywith the abrading roller, so that the loop ofthread drawn into the nozzle is taken up thereby.

Forwarding means 172 preferably includes both a positive forwarding means (e.g. a driven roller pair) and an air stream to direct the yarn end to the nozzle in means 174. Package 171 is replaceablysupported on a carrier i 69 mounted in tl. tended and enabling required withdrawal ofyarn from the package. The forwarding means is operated to forward thread from package 171 until the yarn has been clamped by clamp 124. The suction nozzle in means 174 draws yarn continuously, but is of course ineffective to movethethread while either of clamps 124,134 is effective.

As soon as yarn withdrawal from the spinning unit commences, manipulating device 174 is moved by means (notshown)to connecttheyarnto a bobbin tube inthewindup system. Devices to enable this are known in the art, and will not be described here. A novel deviceforthis purpose is described in ourco pending British PatentApplication No. (entitled "Bob bin Inserting Device" and filed on 20th May1983),the disclosure ofwhich is hereby incorporated in the present specification by reference. However, the present invention is not limited to use in conjunction with the system disclosed in that co-pending application.

Control of movements ofthe means 174 and ofthe centering mechanism 196 is effected by the cam set 123 referred to above. Control of the application of suction and ofthe knife in the forwarding means 174 is effected by controller 84.

Thus the auxiliary seed yarn is introduced to the main piecing system at the most convenient stage thereof, namely immediately prior to the threading step. Mechanism 96 and nozzle 90 can be considered as arranged to present an accessible length of seed yarntothethreading element, and the manipulating means 174 bringsthe auxiliary seed yarn into operative relationship with this presenting means.

The clamping means 124and 134can beofsub stantially similar construction, each preferably being arranged to apply a controlled clamping pressureto the yarn. The basic principles of a suitable clamp construction are shown in Figure 14. A carrier part 173 carries a pivotally mounted clamping element 175. A dogleg lever 177 is pivotally mounted on the carrier 173 and 179. One leg ofthe lever carries a clamping element 180 having a surface adapted to co-operate with the clamping element 175. The other leg ofthe lever is pivotallyconnected to an operating rod 182 operable by a cam follower from the cam set (for clamp 134alsofrom the nip roll release).Element 175 has a tail portion 184 and the element is biased (by means not shown) so that the tail portion retains contact with the dog-leg lever 177 as the latter is pivoted to open the clamp (illustrated condition). The yarn is guided to a position between the clamping elements by a centering slot 186 with the clamp open.

Lever 177 is then pivoted anti-clockwise as viewed in Figure 14 on its mounting 179, and element 175 is pivoted clockwise on its mounting because ofthe contactoftail 184with lever 177. The clamping elementscome into contact at the line 188 in Figure 14so that the yarn is clamped between the rounded surfaces of the elements 175, 180. It is released by reverse pivotal movement of the dog-leg lever on the fixed carrier 173.

Initiation offiberfeed may be effected by closing a reed switch operable to energize/de-energize an elec tromagnetically operated clutch 28. The reed switch may be under the control of the yarn monitor 48 and the piecer may be provided with means to operate the yarn monitor despite the absense of a yarn during the piecing operation. Operation of the yarn monitor is, however, preferably effected in a contact-free manner; the principles of such operation are well known, see for example US Specification 4091606. Accordingly, detailed description is omitted in this Specification.

The position ofthe lever 66 at the time of contact with lever 86 (figure 3) on the piecer can be registered as follows. Lever 86 carries at its free end a proximity switch (not shown) which indicates contactof lever 86 with lever 66. Operation ofthe proximity switch oper ates a clamp (not shown) inside the unit 88 to register the position of lever 66. However, the clamp (and hence levers 86 and 66 now associated therewith) is movablethrough a short additional stroke in the cylinder, sufficient to release the machine lift-offsys tem. The clamp then travels in reverse through its additional stroke returning arm 66 to the registered position.

Where it is considered necessary to piece at "low speed " (i.e. art a speed substantially below the normal operating speed), the starting signal for starting the final stage of the piecing operation may be triggered by reference to sensed rotor speed instead of merely by reference to completion of preliminary operations.

The control means therefore responds to the condition of the spinning unit (as represented by rotor speed or completion of preparation operations on the unit)toissuethestartsignal.

Means may be provided to reduce rotor speed from normal to the desired level - preferably by cancelling rotor drive for a brief period. Rotor speed is preferably as near constant as possible during the final piecing stages. Yarn withdrawal is preferably timed in relation to the start signal.

Claims (25)

1. A method of piecing a machine of the type described by means of a travelling piecing apparatus, comprising the steps of seperating said nip roll pair, threading a seed yarn with the nip roll pair, feeding the seed yarn back to the rotor to join with a fiber ring therein, and withdrawing the seed yarn and newlyformed yarn pieced thereto by re-engaging said nip roll pair, said feeding and withdrawing steps being effected while the rotor is operated at or close to the selected operating speed.

2. A method as claimed in claim 1 wherein said seed yarn is provided by a broken yarn end on a package at said packageforming means.

3. A method as claimed in claim 1 or claim 2 wherein said selected operating speed lies in the range 40'000 - 85'000 RPM, especially 60'000 - 85'000.

4. A method as claimed in any of claims 1 to 3 including the step of initiating withdrawal of the seed yarn upon expiry of a predetermined time interval measured from a predetermined start signal.

5. A method as claimed in any of claims 1 to 4 including the step of clamping the seed yarn at a location downstream from the nip rolls until reengagement of said nip rolls.

6. A method as claimed in any of claims 1 to 5 including the step of forming a yarn reserve in said seed yarn, forming a prepared end on said seed yarn and prelocating said prepared end relative to the spinning unit priortofeeding back yarn from said reserve.

7. A method as claimed in any preceding claim comprising the step of creating relatively wide separ- ation between said nip rolls forthreading of said seed yarn therewith and maintaining a relatively small separation of said rolls during said back feed ofthe seed yarn.

8. Atravelling piecing apparatusforamachine of the type described comprising means for separating said nip rolls, means forforming a yarn reserve in a seed yarn and operablecontrollablyto release said reserveforbackfeed into the spinning unit, meansfor initiating operation of said feed means, and control means responsiveto the condition of the spinning unit and operable when the spinning unit is in a predetermined condition to initiate in a predetermined sequence operation ofthefeed means, operation of said yarn reserve means to release said reserve and re-engagement of said nip rolls to effectwithdrawal of seed yarn and newly spun yarn pieced thereto, said control means including timing means to time initiation of said re-engagement from a predetermined timing reference.

9. Apparatus as claimed in claim 8 wherein said timing means is operable to time initiation of operation oftheyarn reserve means from the same timing reference.

10. Apparatus as claimed in claim 8 or claim 9 wherein said control means is operable to initiate said sequence afterthe spinning unit has reached its selected operating speed.

11. Apparatus as claimed in anyof claim 8to 10 wherein said separating means comprises releasable retaining means operable to retain said nip rolls in a separated condition againstthe effect of bias means urging the nip rolls towards the engaged condition.

12. Apparatus as claimed in claim 11 wherein said separating means comprises means operable to produce a relatively large spacing between the nip rolls forthreading of a seed yarn therewith, said retaining means being operable to maintain a relatively small spacing between the nip rolls.

13. Apparatus as claimed in any of claims 8 to 12 wherein said reserve means comprises biasing means urging release ofyarn in the reserve and retaining means operable to retain the reserve against the effect of the biasing means.

14. Apparatus as claimed in any of claims 8to 13 including means to define a predetermined length of seed yarn threaded with said nip rolls and with said reserve means and means to manipulate said seed yarn into the spinning unit, the reserve means being operable during manipulation of the seed yarn to maintain said length of yarn taut.

15. Atravelling piecing apparatusfora machine ofthe type described comprising means for controllably separating said nip roll pair, means for threading a seed yarn with the separated nip rolls and yarn clamp means operable to clamp the seed yarn at a location downstream from the nip rolls and to release the seed yarn upon re-engagement of the nip rolls.

16. Apparatusas claimed in claim 15wherein said location is adjacent said nip rolls.

17. Atravelling piecing apparatusfora machine ofthe type described comprising, meansforforming an accessible length of seed yarn, meansforforming a reserve for backfeed of seed yarn tothe spinning unit, means to separate said nip rolls, and threading means movable on a predetermined path intersecting said accessible length of seed yarn to collect said seed yarn and thread it with the nip roll pair and reserve forming means.

18. Apparatus as claimed in claim 17 wherein said meansforforming an accessible length of seed yarn comprises end finding meansforfinding a broken end on a yarn wound up on said package forming means.

19. Apparatus as claimed in claim 17 or claim 18 and further comprising means to form a predetermined end portion on said seed yarn, said threading means being operable to bring the seed yarn into operable relationship with said end forming means.

20. Apparatus as claimed in any of claims 17 to 19 wherein said meansforforming an accessible length of seed yarn comprises yarn guide means movable across a predetermined zone in which said yarn could be located to collect said seed yarn and then movable to a predetermined position to hold said seed yarn for collection by said threading means.

21. Apparatus as claimed in any of claims 17 to 20 wherein said threading means comprises an elongate member extending cantilever-fashion from a movable mounting therefor, said memberhavingayarn guiding means adjacent its free end.

22. A method of piecing a machine of the type described by means of a travelling piecing apparatus comprising the steps of separating said nip roll pair, threading a seed yarn with the nip roll pair, forming a reserve in said seed yarn, feeding seed yarn from said reserve back to the rotor to join with a fiber ring therein, withdrawing the seed yarn and newly formed yarn pieced thereto by re-engaging said nip roll pair, and defining a predetermined time period during which said backfeed of seed yarn occurs and at the expiry of which withdrawal of seed yarn is commenced.

23. A method as claimed in claim 22 including the step of maintaining the speed ofthespinning unit constant during said period.

24. A method as claimed in claim 23 wherein the spinning unit is operated at its selected operating speed during said period.

25. An apparatus asclaimed in claim 15 orclaim 16 including meansforforming a yarn reserve in said seed yarn, means for defining a predetermined length of seed yarn extending from said yarn clamp means, and means to manipulate said length of seed yarn into the spinning unit, the reserve means being operable during manipulation of the seed yarn to maintain said length ofyarntaut.