US3821878A

US3821878A - Open-end textile spinning machines

Info

Publication number: US3821878A
Application number: US00205684A
Authority: US
Inventors: R Parsons
Original assignee: Platt International Ltd
Current assignee: Hollingsworth UK Ltd
Priority date: 1970-12-11
Filing date: 1971-12-07
Publication date: 1974-07-02
Anticipated expiration: 1991-07-02
Also published as: ES397847A1; CH547875A; FR2118050B1; FR2118050A1; CS181217B2; GB1376110A; DE2161642A1; IT945337B

Abstract

SHORTENED PATH, TO CONVEY IT TO THE YARN HOLDING MEANS AND TO SURRENDER THE YARN THERETO TO REFORM THE EXTENDED YARN PATH. THE YARN ENGAGING MEMBER MAINTAINS THE EXTENDED POSITION DURING SAID FIRST MOVEMENT ONLY WHEN CONVEYING YARN TO THE YARN HOLDING MEANS AND RETRACTING TO THE RETRACTED POSITION IN THE ABSENCE OF YARN IN THE SHORTENED PATH AND UPON SURRENDER OF THE YARN TO THE YARN HOLDING MEANS.

AN OPEN-END SPINING MACHINE COMPRISES A SPINING STATION AT WHICH FIBERS ARE FED IN DISCRETE FORM TO A FIBER COLLECTING SURFACE OF A SPINNING ROTOR AND WITHDRAWN IN THE FORM OF SPUN YARN BY YARN TAKE-UP MEANS. THERE IS PROVIDED YARN PIECINGUP APPARATUS COMPRISING A YARN RESERVE-LENGTH HOLDING MEANS WHICH HOLDS THE YARN DURING NORMAL SPINNING IN AN EXTENDED PATH BETWEEN THE SPINNING ROTOR AND THE YARN TAKE-UP MEANS AND FROM WHICH THE YARN CAN BE RELEASED SO AS TO FOLLOW A SHORTENED PATH THEREBY TO ENABLE THE END OF YARN TO RETURN TO THE FIBER COLLECTING SURFACE AND TO CONTACT AND TWIST IN THE FIBERS THEREON. A YARN RESERVE-LENGTH FORMING MEANS INCLUDES A RECIPROCATING FIRST MOVEMENT BETWEEN A POSITION ADJACENT A YARN IN THE SHORTENED PATH AND A POSITION ADJACENT A YARN HOLDING MEANS AND A SECOND MOVEMENT DURING A PART OF THE SAID RECIPROCATING MOVEMENT IN WHICH THE YARN ENGAGING MEMBER MOVES FROM A RETRACTED POSITION WHERE IT MAKES NO CONTACT WITH THE YARN TO AN EXTENDED POSITION TO ENGAGE A YARN IN THE

Description

United States Patent [1 1 [111 3,821,878 Parsons 1 ;July 2, 1974 OPEN-END TEXTILE SPINNING MACHINES station at which'fibers are fed in discrete form to a [75] Inventor: Ronald Parsons, Rishton, England fiber collecting surface of a spinning rotor and withdrawn in the form of spun yarn by yarn take-up [73] Assignee: Platt International Limited, Oldham, means, There is provided yarn piecing-up apparatus WW g England comprising a yarn reserve-length holding means which holds the yarn during normal spinning in an extended [22] Flled 1971 path between the spinning rotor and the yarn take-up [21] Appl. No.: 205,684 means and from which the yarn can be released so as to follow a shortened path thereby to enable the end of yarn to return to the fiber collecting surface and to [30] Foreign Apphcatmn Priority Data contact and twist in the fibers thereon. A yarn reserve- Dec. 11, 1970 Great Britain 58,987/70 length forming means-includes a reciprocating first movement between a position adjacent a yarn in the [52] US. Cl. 57/34 R, 57/5895 Shortened path and a position adjacent a yam holding [51] Int. Cl D0lh 15/00 means and a Second movement during a part f the [58] Field of Search 57/34 R, 58.89,v 58.95 Said reciprocating movement in Whhsh the yam ehgag ing member moves from a retracted position where it References C'ted makes no contact with the yarn to an extended posi- UNITED STATES PATEN tion to engage a yarn in the shortened path, to convey 3,680,300 8/1972 Landwehrkamp 57/34 R it to the y holding means and to surrender the y 3,354,631 11/!967 Elias et al. 57/5895 thereto to reform the extended yarn path. The yarn 3,455,095 7/1969 Makeham et al. 57/34 R engaging member maintains the extended position 3.685.267 8/1972 Landwehfkamp at 57/34 R during said first movement only when conveying yarn Primary Examiner.lohn Petrakes Attorney, Agent, or Firm-Watson, Cole, Grindle & Watson [57] ABSTRACT An open-end spinning machine comprises a spinning to the yarn holding means and retracting to the retracted position in the absence of yarn in the shortened path and upon surrender of the yarn to the yarn holding means.

14 Claims, 7 Drawing Figuresv PATENTEUJUL 2 I874 SHEET 3 1F 3 1 OPEN-END TEXTILE SPINNING MACHINES The present invention relates to open-end spinning machines for textile yarns.

In particular, the invention relates to an open-end spinning machine of the type in which fibres are fed in discrete form to a fibre collecting surface of a spinning rotor and withdrawn in the form of spun yarn by yarn take-up means.

It has hitherto been proposed to provide in machines of this type a reserve length of yarn between the spinning rotor and the yarn take-up means, which is available during normal spinning. Upon end breakage or upon a reduction in yarn tension or upon re-starting spinning after machine stoppage, the reserve length of yarn is released so that the yarn follows a shortened path to enable the tail end of yarn to return to and contact and twist in fibres on the fibre-collecting surface of the spinning rotor, thereby effecting a piecingup operation, which in the event of end breakage is carried out without interruption of the spinning process.

Following the piecing-up operation, the reserve length must be reformed in readiness for any subsequent end breakages or reductions in yarn tension or for subsequent rc-starting of the machine.

It has been found that the reserve-length forming ar-,

rangements of yarn piecing-up apparatus hitherto proposed have proved unsatisfactory when used in openend spinning machines required to produce yarns on a commercial scale.

It is an object of the present invention to provide in an open-end spinning machine of the type specified improved automatic yarn-piecing apparatus.

According to the present invention, there is provided an open-end spinning machine comprising a spinning station at which fibres are fed in discrete form to a fibre collecting surface of a spinning rotor and withdrawn in the form of spun yarn by yarn take-up means and at which there is provided yarn piecing-up apparatus comprising a yarn reserve-length holding means which holds the yarn during normal spinning in an extended path between the spinning rotor and the yarn take-up means and from which the yarn can be released so as to follow a shortened path thereby to enable the end of yarn to return to the fibre collecting surface and contact and twist in the fibres thereon, and a yarn reserve-length forming means including a reciprocable yarn engaging member arranged to carry out a reciprocating movement to convey a yarn in the shortened path to the yarn holding means, the arrangement being such that the yarn engaging member moves during a part of the said reciprocating movement from a retracted position where it makes no contact with the yarn to an extended position to engage a yarn in the shortened path, to convey it to the yarn holding means and to surrender the yarn thereto to reform the extended yarn path, the yarn engaging member maintaining the extended position only when conveying yarn to the yarn holding means and retracting to the retracted position in the absence of yarn in the shortened path and upon surrender of the yarn to the yarn holding means.

Preferably, the yarn engaging member is attached to a reciprocal carriage and control means are provided to cooperate with said yarn engaging member to cause said member to move only to the extended position to engage said yarn in the shortened yarn path and to retract in the absence of yarn in the shortened yarn path and when the extended yarn path is established and the yarn released from the yarn engaging member.

Preferably, the reciprocal carriage carries a plurality of yarn-engaging members serving a plurality of spinning stations of the machine.

Some embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a front elevation of yarn piecing-up apparatus of an open-end spinning machine according to a first embodiment of the invention,

FIG. 2 is a plan partly in section of the apparatus shown in FIG. 1, with some of the parts removed for clarity,

FIG. 3 is a sectional plan drawn to an enlarged scale of a loop forming mechanism forming part of the apparatus shown in FIGS. 1 and 2,

FIG. 4 is a section of the apparatus shown in FIG. 3, taken on the line IVIV in FIG. 3,

FIG. 5 is a rear elevation of the apparatus shown in FIG. 3,

FIG. 6 is a front elevation of yarn piecing-up apparatus of an open-end spinning machine according to a further embodiment of the invention, with parts thereof removed for clarity, and

FIG. 7 is a plan partly in section of the apparatus shown in FIG. 6.

As seen in FIGS. 1 and 2, spun yarn I is withdrawn from the fibre-collecting surface of a spinning rotor (not shown) through a doffing tube 2 by means of

delivery rollers

3 and 4. Between the doffing tube 2 and the

delivery rollers

3 and 4, the yarn contacts a sensing arm 5 of a yarn-tension detecting switch,'the function of which will hereinafter be described.

From the

delivery rollers

3 and 4 the spun yarn 1, during spinning, normally follows-a path around an upper arm 6 ofa fixed guide 7, around a hook portion 50 of a latch 8, and then around a lower arm 9 of the fixed guide 7, after which the yarn is collected on a package in the conventional manner. An extended yarn path is therefore provided by forming a reserve loop around the latch 8, which serves as a reserve-loop holding member. Conveniently, the fixed guide 7 and the latch 8 are fixedly attached to a housing 10, which houses a yarn reserve-loop releasing mechanism 11 fixedly attached to the machine frame.

The loop releasing mechanism 11 includes a solenoid 12, through the centre of which passes an actuating rod 13, which moves in response to energisation of the solenoid. The actuating rod 13 extends from the left-hand end of the solenoid 12, as seen in FIGS. 1 and 2, and is bent through a right angle to form an arm 14, which passes through a slot 15 in the lower end of a lever-16 pivotally supported at its upper-end by trunnions 17 and 18 which extend from each side of the lever 16 at right angles thereto. The .trunnions l7 and 18 have their ends conically reduced so that they accurately lo- ,cate in seatings formed in bearings 19 and 20, which are so mounted in the housing 10 that the distance between them can be adjusted to ensure accurate location. Fixedly attached to the supporting trun'nion 17 is a boss 21, which carries the lower end of a yarn deflecting arm 22 extending upwardly through a slot 23 formed in the housing 10. The deflecting arm 22 passes upwardly in front of the driving roller 4, and then downwardly towards the nip formed between the

rollers

3 and 4 so that a hooked end portion 24 thereof encompasses the yarn 1.

The actuating rod 13 also extends from the solenoid 12 at the right-hand end thereof, as seen in FIGS. 1 and 2, and has mounted on this end a tongue operating arm 25. Between the tongue operating arm 25 and the solenoid 12 there is arranged a compression spring 26,

which biases the rod 13 to the right, bringing a stop 151 on the rod 13 to bear against the left-hand end of the solenoid 12. The tongue operating arm 25 is formed with a closed slot through which passes 21 depending arm of a tongue member 27 which is in the form of a cranked lever pivotally connected to the latch 8 at the point 28. The latch 8, as seen in FIG. 4, is formed with two side pieces between which the tongue 27 is pivotally mounted.

The loop releasing mechanism 11- is arranged to operate when a decrease in tension in the spun yarn occurs. This decrease in tension is detected by the sensing arm of the yarn-tension detecting switch which causes encrgisation of the solenoid 12. Upon energisation of the solenoid 12, the actuating rod 13 moves to the left, as seen in FIGS. 1 and 2, with a force sufficient to overcome the biasing force of the spring 26. As the actuating rod 13 moves to the left, the arm 14 engaging the slot 15 causes the lever 16 and the yarn deflecting arm 22 to pivot about the bearings 19 and 20 in a clockwise direction. The yarn 1 is thus engaged by the hooked end portion 24 of the yarn deflecting arm 22 and is removed out of the nip formed between the

delivery rollers

3 and 4 so that momentarily they cease to withdraw the yarn through the doffing tube 2. At the same time, the tongue operating arm 25 on the actuating rod 13 moves to the left and causes the tongue .member 27 to pivot in a clockwise direction. the

tongue member 27 releases the yarn from the latch 8 so that the path of the yarn is shortened, which enables the tail end of yarn to return to contact and to twist in fibres 0n the collecting surface of the spinning rotor, thereby effecting an end breakage repair. The solenoid 12 is energised only momentarily and the spring 26 subsequently causes the actuating rod 13 to return to its inoperative position. As this happens, the hooked end portion 24 of the yarn deflecting arm 22 returns and the yarn 1 reverts into the nip between

delivery rollers

3 and 4 so that delivery of spun yarn recommences.

The release of yarn can, of course, be effected on starting the spinning operation by pulsing solenoid l2 such that the yarn is removed from the latch 8 thereby enabling the tail end of yarn to contactand twist in fibres on the fibre collecting surface of the spinning rotor.

The yarn is now following a shortened yarn path and it will be appreciated that the reserve loop must be reformed in readiness for release upon any subsequent decrease in yarn tension or for starting following machine stoppage. This is effected by a loop re-forming mechanism which comprises at each spinning station a yarn pick up mechanism 136 arranged in .a slot 30 of a carriage bar 29 common to all the stations and extending along the length of the machine behind the loop releasing mechanism 11. As best shown in FIGS. 3, 4 and 5, the yarn pick-up mechanism at each station comprises a yarn pick-up arm 31 which is pivotally supported on trunnions 32 and 33which protrude from the sides of the arm 31- and which are formed with conical ends which engage in

bearings

34 and 35. The pick-up arm 31 is provided at one end with a yarn engaging end portion 36 and at the other end with a counterbalance portion 37 to ensure fine balancing of the arm. Also mounted within the slot 30 is a two-armed lever 140 provided with supporting

trunnions

38 and 39 having conically formed ends which engage in

bearings

40 and 41 located in opposite sides of the slot 30. One arm 42 of the two-armed lever 140 is bent so that it engages in a slot 43 provided in the yarn pick-up arm 31, and the other-arm 44 extends outside the periphery of the bar 29. Attached to the arm 44 is one end of a tension spring 45 which tends to bias the two-armed lever 140 in an anti-clockwise direction as seen in FIG. 3. The other end of the spring is anchored to a peg 46 which is located in a bore 47 by a screw 48.

In operation, the loop-forming mechanism functions as follows. In the preferred embodiment of the invention as illustrated, the carriage bar 29 continuously moves to and fro during the entire spinning operation. When a reserve loop of yarn has been released from the latch member 8 and the carriage bar 29 is moving on a return stroke in the direction indicated by arrow A (see FIG. 2), the yarn pick-up mechanism 136 would be in a retracted position indicated in broken lines as shown in FIGS. 2 and 3 due tothe action of spring 45 on the trip arm 44. As the yarn pick-up mechanism ap proaches the yarn l, the trip arm 44 comes into contact with a stop 49 which causes the two-armed lever 140 to pivot on

trunnion arms

38 and 39, overcoming the force of spring 45, so that it takes up the position shown in full lines-in FIG. 3. The pivotal movement ofthe arm 42 of the lever l40,'by its engagement with slot 43 in the yarn pick-up arm 31, causes the yarn-engaging end portion 36 to protrude from the side of the carriage bar 29. Continued travel of the bar 29 in the direction of the arrow A causes the yarn-engaging portion 36 protruding therefrom to pass between

guide arms

6 and 9, with the yarn 1 riding over the portion 36, and after a further short travel the bar 29 reaches the end of its return stroke.

The bar 29 then commences its loop forming stroke in the direction of arrow B (see FIG. 2) and as the yarn engaging portion 36 passes between

guide arms

6 and 9 it picks up the yarn 1 and begins to take it towards the latch 8. The trip arm 44 disengages from the stop 49 but the mechanism is held in position by the tension in the yarn which is sufficient to overcome the force of spring 45. The yarn 1 is therefore conveyed over the hook portion 50 of the latch 8 until the bar 29 reaches the end of the loop forming stroke. On a further return stroke of the bar 29 the yarn is caught by the hook portion 50 which retains the yarn and provides a reserve length of yarn available for release during any subsequent decrease in yarn tension.

As soon as the yarn engaging portion 36 is relieved of the yarn tension, the force in the spring 45 causes the mechanism to assume the retracted position i.e., as shown in broken lines in FIGS. 2 and 3. Thus, ifa decrease in yarn tension should re-occur at this spinning station or at any other spinning station whilst the carriage bar 29 returns, the yarn engaging portion 36 would not prevent the reserve-length of yarn from being completely released to the shortened path. It will be appreciated that if the yarn does not completely return to the shortened path, successful piecing will not be accomplished.

stop 49 the action of the spring 45 causes the yarn engaging portion 36 to retract into the slot 30. Thus it will be seen that, as the carriage bar 29 conveys the yarn engaging portion 36 towards the latch 8 in a disposition in which it is out of the plane containing the yarn in the extended path, the yarn-engaging portion 36 would not prevent the yarn from being released to the shortened path should a decrease in yarn tension be detected.

It will be seen that the arrangement gives the advantage that during reciprocation of the loop forming mechanism at no time is the yarn engaging portion 36 in a position in which it would interfere with a yarn during release of. the latter to the shortened path.

Although the carriage bar 29 preferably reciprocates continuously during the spinning process, it could be arranged for movement of the carriage to be initiated only when detection of a reduction in tension of the spun yarn occurs.

Preferably, the arrangement is such that the speed of the carriage bar 29 during the return stroke is greater than the speed of the bar during the loop forming stroke.

In the embodiment of the invention illustrated in FIGS. 6 and 7 the reserve length of yarn is formed at a position between the doffing tube 2 and the

delivery rollers

3 and 4.

Referring first to FIG. 6, spun yarn l is withdrawn from the fibre-collecting surface of a spinning rotor (not shown) through a doffing tube 2 by means of

delivery rollers

3 and 4. After emergence from the doffing tube 2 the spun yarn, during spinning, normally follows a path around an upper fixed guide 51, around a hook portion 52 and then around a lower fixed guide 51'. The yarn then passes through the delivery nip provided by the

delivery rollers

3 and 4 to be delivered thereby and collected on a package in a conventional manner. An extended path is thereby provided during normal spinning by forming a reserve loop around the hook portion 52.

Referring now to FIG. 7, the hook portion 52 is formed on one end ofa yarn holding arm 53 which constitutes part of a yarn reserve-loop holding mechanism 54. The yarn reserve-loop holding arm 53 is pivotally mounted at 55 to a bracket 56 and has a counterbalance portion 57 provided at the end opposite to the hook portion 52 to ensure fine balancing of the arm. Also pivotally mounted on the bracket 56 at 59 is a twoarmed lever 58 one arm 60 of which is bent so that it engages in a slot 61 provided in the arm 53. A trip arm 62 extends outwardly and functions in a manner hereinafter described. The trip arm 62 is engaged by one end of a tension spring 63 the other end of which is anchored to a tension adjusting screw 64 which can be turned to alter the tension in the spring 63. The spring 63, therefore, tends to turn the two-arm lever 58 in an anti-clockwise direction (as seen in FIG. 7) which causes the arm 53 to pivot about the point 55 in a clockwise direction (as seen in FIG. 7). However, during normal spinning the tension in the yarn is sufficient to overcome the effect of the spring 63 and the arm 53 is thereby held in the position shown in FIG. 7.

Should a reduction in yarn tension or end breakage occur, the spring 63 causes the two arm-lever 58 to turn in an anti-clockwise direction. The end of the arm 60 slides down the slot 61 and causes the arm 53 to pivot in a clockwise direction. The yarn is thereby released from the hook portion 52 so' that the path of the yarn is shortened, which enables the tail end of yarn to tween guides 51 and 5], which must be lengthened again in readiness for release upon any subsequent decrease in yarn tension. This lengthening is effected by a loop reforming mechanism 136 arranged in a slot 30 of a carriage bar 29 common to all the stations and extending along the length of the machine. The loop reforming mechanism 136 functions in exactly the same manner as that provided in the embodiment described with reference to FIGS. 1 to 4. As the yarn reforming mechanism approaches the yarn l in the direction of the arrow A the mechanism 136 will be in the retracted position as shown in full line in FIG. 7, until the trip arm 44' comes into contact with a stop 49, which causes the yarn engaging portion 36 to protrude from the side of the carriage bar 29. On the loop forming stroke the carriage 29 moves in the direction of arrow B in FIG. 7 and as the yarn engaging portion 36 passes between fixed

guides

51 and 51 it picks up the yarn l and begins to take it towards the yarn holding arm 53. The trip arm 44 disengages from the stop 49 but the mechanism is held in protruding position by the tension in the yarn which is sufficient to overcome the force of spring 45.

The yarn reserve-loop holding mechanism 54 will be in a retracted position i.e. as'shown in broken lines in FIG. 7 and the hook portion 52 of the yarn holding arm 53 must be returned to a position in which it will engage with the yarn. This is effected by a trip operating member 65 fixedly attached to the reciprocating carriage bar 29, which contacts the trip arm 62 and thus causes the lever 58 to pivot in a clockwise direction, thereby pivotingthe yarn holding arm 53 about the point 55 to place the hook portion 52 in a yarn receiving position. The yarn l is carried slightly beyond the hook portion 52 until the carriage reaches the end of the loop forming stroke. On return of the carriage bar 29 in the direction of arrow A, the yarn l is engaged by the hook portion 52 and-the tension in the yarn is sufficient to hold the mechanism in the position shown in full line when the tripoperating member 65 disengages from trip arm 62. Thus a reserve-length of yarn is available for release during any subsequentdecrease in yarn tension or end breakage. As soon as the yarn engaging portion 36 is relieved of the yarn tension, the force in the spring 45 causes the mechanism 136 to as sume the retracted position as shown in full line in FIG. 7.

In this embodiment it is important to ensure that the speed of the loop forming stroke is such that the count of the yarn is not affected.

What I claim as my invention and desire to secure by Letters Patent is:

1. In an open-end spinning machine comprising a spinning station including a spinning-rotor having a fiber collecting surface, fiber feed means for feeding fibers to the fiber collecting surface in discrete form and yarn take-up means for withdrawing spun yarn from the fiber collecting surface; a yarn piecing-up apparatus comprising:

a. a yarn reserve length holding means for holding the yarn during normal spinning in an extended path between the spinning rotor and the yarn take-up means;

b. yarn release means for releasing the yarn from the yarn reserve length forming means to enable the end of the yarn to return to the fiber collecting surface in a shortened path and to contact and twist in the fibers thereon;

c. a yarn reserve length forming means including a yarn engaging member;

d. first yarn engaging member moving means for moving the yarn engaging member in a reciprocating first movement between a position adjacent a yarn in the shortened path and a position adjacent the yarn holding means;

e. second yarn engaging member moving means for moving the yarn engaging member only when the yarn is in the shortened path in a second movement during said reciprocating first movement between a retracted position in which the yarn engaging member makes no contact with the yarn to an extended position;

wherein the yarn engaging member in the extended position engages the yarn in the shortened path and maintains said extended position while conveying the yarn to the yarn holding means, by said first movement, where the yarn is surrendered to the yarn holding means to form or re-form the extended yarn path.

2. A machine according to claim 1, wherein the first yarn engaging member moving means includes a reciprocable carriage which supports the yarn engaging member and which reciprocates to effect the said reciprocating first movement of the yarn engaging member, and wherein the second yarn engaging member moving means includes displacing means for displacing the yarn engaging member into the extended position during the said part of the reciprocating movement thereof.

3. A machine according to claim 2, wherein the yarn engaging member is pivotable between the retracted and extended positions, and wherein the second yarn engaging member moving means comprises a lever cooperating with the yarn engaging member and pivotal between a first position in which the yarn engaging member takes up the retracted position and a second position in which it holds the yarn engaging member in the extended position and a fixed stop member for engagement by the lever during the said part of the reciprocating movement of the yarn engaging member to pivot the lever from-the first position to the second position.

4. A machine according to claim 3 and further including spring means acting upon the said lever for biasing the yarn engaging member to the retracted position means.

5. A machine according to claim 4, wherein the force of the yarn acting on the yarn engaging member is greater than the force of the yarn engaging member biasing it to the retracted position to hold the yarn engaging member in the extended position throughout its movement to convey the yarn to the yarn holding mem ber.

6. A machine according to claim 2 and further com- .prising control means for responding to movement of a yarn moves to the shortened path to commence the said reciprocating movement of the carriage.

7. A machine according to claim 2 comprising at least one further spinning station at which fibres are fed in discrete form to a fiber collecting surface of a spinning rotor and withdrawn in the form of a spun yarn by yarn take-up means, and at which yarn piecing-up apparatus is provided identical to the yarn piecing-up apparatus provided at the first-mentioned station, and wherein the yarn engaging member associated with the station is supported by the said reciprocable carriage supporting the yarn-engaging member associated with the said first-mentioned station.

8. A machine according to claim 1, wherein the yarn reserve length holding means includes a fixed yarn holding member around which the yarn passes in the extended path and a yarn releasing mechanism for releasing the yarn from the fixed yarn holding member into the shortened path.

9. A machine according to claim 8, wherein the yarn reserve length holding means includes control means for responding to a release signal to operate said yarn releasing mechanism.

10. A machine according to claim 9, wherein the yarn releasing mechanism comprises a displaceable latch and wherein the said control means comprises a solenoid for responding to said release signal to move the said latch to engage the yarn and release it from the yarn holding member.

11. A machine according to claim 9 including a pair of delivery rollers through a hip of which the yarn passes before passing along said extended path, wherein said yarn reserve length holding means includes yarn deflecting means, and said control means is responsive to said release signal and causes said yarn deflecting means to deflect the yarn from a path in which it passes through the nip of the delivery rollers to a path in which it is clear of the nip of the delivery rollers.

12. A'machine according to claim 9, wherein the yarn reserve-length holding means includes a yarntension detecting means responsive to a reduction in yarn tension to generate said release signal.

13. A machine according to claim 1, wherein the yarn reserve-length holding means comprises a yarn holding member for movement between a yarn holding position in which it holds the yarn in the extended path and a yarn release position in which it releases the yarn to take up the shortened path, and biasing means for biasing the yarn holding member to the yarn release position, the tension in the yarn held in the extended path by the yarn holding member maintaining the yarn holding member in the yarn holding position whilea predetermined reduction in tension of the yarn allows the yarn holding member to move to the release position to release the yarn.

14. A machine according to claim 13, wherein the first yarn engaging member moving means includes a reciprocable carriage which supports the yarn engaging member and which reciprocates to effect the said reciprocating first movement of the yarn engaging memher, and wherein the second yarn engaging member moving means includes displacing means for displacing the yarn engaging member into the extended position during the said part of the reciprocating movement 9 10 thereof, wherein the yarn reserve-length holding means the excursion of the carriage during which the yarn is comprises stop means carried on said carriage for dissurrendered to the yarn holding member by the yarn placing the yarn holding member from the yarn release engaging member. position-to the yarn holding position during that part of