GB2039552A - An automatic device for replacing full bobbins by empty spools in a yarn-winding system - Google Patents

Abstract

Automatic doffing and replacement of bobbins by empty spools is carried out without any interruption of spinning operations by means of a device comprising a carriage and photoelectric means for detecting a full bobbin as the carriage passes in front of a winding unit and for actuating means locking the carriage in position. The yarn is cut between the bobbin and the delivery roller and the delivery end is retained. The bobbin guiding arms are lifted and opened-out for discharging the full bobbin and receiving an empty spool taken from a magazine, then lowered until the spool rests on the yarn-winding roller, and a yarn reserve is formed on the spool by means of a suction nozzle, all operations being controlled by a programmer mounted on the carriage.

Description

SPECIFICATION Automatic spool replacement device for textile machine having yarn-winding system This invention relates to an automatic device for doffing bobbins of yarn and replacing said bobbins by empty spools with formation of a yarn reserve on a machine for forming cylindrical or conical bobbins such as a spinning frame, a winding frame or a finisher, for example. In a machine of this type, each yarn-winding unit is surmounted by a winding roller.

A spool applied against said roller is guided between two arms which are capable of pivoting on a horizontal shaft under the action of gravity and of opening-out to a slight extent in order to permit doffing of a full bobbin and replacement of this latter by an empty spool.

The device according to the invention permits automatic doffing of bobbins without interrupting spinning operations or either tangential or axial unwinding of bobbins. Said device comprises a carriage so arranged as to move along a rail having a configuration which enables said carriage to pass successively in front of all the yarn-winding units of the machine.Said carriage is in turn provided with a drive motor for propelling the carriage along the rail, means for detecting a full bobbin within a winding unit as the carriage passes in front of said unit, means for locking the carriage in front of said winding unit in response to a signal emitted by said means for detecting a full bobbin, means for lifting the full-bobbin guiding arms and for allowing said arms to return downwards with an empty spool until said spool rests on the yarn-winding roller, means for cutting the yarn between the delivery roller and the bobbin, means for opening-outthe bobbinguiding arms in order to release said bobbin and for closing said arms against an empty spool, an empty-spool magazine, meansfortaking an empty spool from the magazine and placing said spool between the guiding arms aforesaid.The machine further comprises means for retaining the end of that portion of yarn which is connected to the delivery roller, the retained portion of yarn being located in front of the delivery and winding rollers but behind the empty spool; and the carriage further comprises a programmer for controlling all the means aforementioned.

By means of this device, practically continuous operation of the machine is achieved without any need to interrupt the movement of rotation of the winding rollers in order to replace bobbins, this operation being performed in a fully automatic manner.

Abetter understanding of the invention will be gained from the following description and from the accompanying drawings which show by way of example one embodiment of a device according to the invention for automatically doffing yarn bobbins and replacing said bobbins by empty spools on a freed-fiber spinning frame.

In these drawings: Figure 1 is a profile view of the complete device; Figure2 is a corresponding partial plan view; Figure 3 shows the mechanism for controlling the backward and forward motion of the suction nozzle; Figure 4 shows the mechanism for controlling the up-and-down motion of the suction nozzle; Figures 5 and 6 illustrate the yarn-cutting device in two different positions; Figure 7shows the mechanism for controlling the lifting and lowering of the yarn-winding arm; Figure 8 is a corresponding partial plan view; Figure 8A shows another position of the elements illustrated in Figure 8; Figure 9 illustrates the mechanism for feeding and gripping empty spools; Figure 10 is a sectional view of the suction nozzle showing the mechanism for cutting the yarn reserve; Figure 11 shows the empty spool magazine;; Figure 12 to 16 illustrate in perspective the successive steps of one cycle of the installation; Figure 17 is a partial plan view to a larger scale showing a feeler looking in the direction of the arrows XVII-XVII of Figure 1; Figure 18 is a partial plan view which is also to a larger scale and shows a safety hook looking in the direction of the arrows XVIII-XVIII of Figure 1; Figure 19 shows the hook of Figure 18 in another position.

The device which is illustrated in simplified manner in profile in Figure 1 and in plan in Figure 2 is intended to carry out automatically the doffing of yarn bobbins and positioning of empty spools on a freed-fiber spinning frame without interrupting the process of spinning or unwinding of the yarn either tangentially to the bobbin or axially.

The device according to the invention comprises a carriage 1 provided at the top with runner-wheels 2 which roll on a top horizontal rail 3 and at the bottom with runner-wheels4which roll against a horizontal bottom rail 5. Said carriage is thus capable of passing successively in front of all the spinning stations 11 and corresponding yarn-winding stations 7 as it travels around the entire machine.Each yarn-winding unit 7 comprises: a delivery roller 12 with its press roller 13 carried by a rocker-arm 14; a winding roller 17 which supports and drives in rotation the bobbin 21 formed bytheyarn 22 delivered by the spinning unit 11; a system of two arms 23, 24 pivotally mounted on a horizontal pin 25 (as also shown in Figure 12) to which further reference will be made hereinafter and which serve to position the yarn bobbin 21 on the winding roller 17 by means of two pivot-pins 27, 28 which are rigidly fixed respectively to the two arms 23, 24 and engaged in the two ends of a spool 30 which carries the bobbin 21; a yarn guide 26 (Figure 12) which is capable of displacement in reciprocating motion in front of the winding roller 17; and an inclined plane 28 (Figure 11) forthe removal of full bobbins 29.

The displacements of the carriage 1 on its rails 3,5 are produced by a reduction-gear electric drive motor 32 which is carried by the carriage 1 and the output shaft 33 of which is coupled to the runnerwheels 2. Supply of current to the electric motor 32 is carried out by means of a system of friction shoes 34 which slide on a fixed supply rail 35 carried by the runner-rail 3. The motor 32 always drives the carriage 1 in the same direction of travel around the machine. The circuits for supplying current to the electric drive motor 32 are controlled by a programmer 38 having electric contacts actuated by cams and driven in rotation by an electric motor 39 which is also carried by the carriage 1 and controlled by said programmer.

A photoelectric cell 42 mounted on the carriage 1 emits a signal during its travel and as it passes in front of a bobbin 21 which has reached the maximum desired diameter in order to stop said carriage as well as to initiate the process of doffing of the full bobbin and replacement of this latter by an empty spool. By way of alternative, the signal can be produced, for example, by a feeler 33 which is also carried by the carriage and intended to be caught by the tip of an extension 24A of the bobbin positioning arm 24 as said carriage moves past the feeler.

Whichever arrangement is adopted, the emission of said signal has the effect of interrupting the supply of current to the electric motor 35 which drives the carriage and causing the engagement of a movable locking-bolt 46 carried by the carriage 1 within a box staple or bolt clasp 47 which is fixed against the top runner-rail 3. Thus the carriage is temporarily but securely maintained stationary on its rails and positioned with accuracy in front of the spinning station 7 considered.

A suction nozzle 51 (as also shown in Figures 3 and 4) is pivotally mounted by means of a pin 52 on an arm 53 which is in turn pivotally mounted on the carriage 1 by means of a pin 54. The nozzle 51 has an extension 51Awhich is subjected to the action of a cam 56 for controlling the up-and-down movements of the nozzle as well as to the action of a spring (not shown) for returning the nozzle extension towards the cam. The arm 53 is provided with an extension 53A which is subjected to the action of a cam 58 for controlling the backward and forward movements of the nozzle and to the action of a spring (not shown) for returning said arm extension towards the cam.

The two cams 56 and 58 are fixed on a camshaft 59 rotatably mounted within the carriage 1 and coupled to the shaft of the electric motor 39 which already serves to drive the electric programmer 38. A partial vacuum is applied to the suction nozzle 51 through a flexible hose 62 under the action of an induced-draft fan 63 mounted on the carriage 1 (as shown in Figure 1).

Within the end portion of the suction nozzle 51, a curved thread-cutting blade 66 (shown in Figures 5 and 6) fitted with a hook 67 is pivotally mounted by means of a pin 68 and urged by a torsion spring 71 to carry out a pivotal movement in the clockwise direction or in other words in the direction of the arrow f1 in Figure 5 so as to cut the yarn 22 and reach the angular position shown in Figure 6. The threadcutting blade 66 can be restored to its initial angular position of Figure 5 in opposition to the force of the spring 71 by means of an electromagnet 73 mounted within the suction nozzle 51 and adapted to produce action on a connecting-rod 74. One end of said connecting-rod is pivoted to an extension 66A of the thread-cutting blade 66 by means of a pin 75 and the other end is adapted to slide within a pivoting nut 76 mounted within the nozzle.

The vertex of a bell-crank lever 79 (shown in Figures 7 and 8) is pivotally mounted on a horizontal pin 81 carried by the carriage 1. One of the arms 82 of said lever is subjected to the action of a cam 83 fixed on the camshaft 59 and to the action of a spring (not shown) for returning said arm towards the cam.

The other arm of said lever is constituted by a blade of spring steel which has the configuration shown in Figure 8 in the free state. An electromagnet 87 carried by the carriage 1 is capable of thrusting-back the arm 85 in the direction of the arrow f2 (Figure 8) as shown in Figure 8A. The end of the arm 85 carries a stud 89 which is adapted to lift the end portion of the extension 24A of the bobbin-positioning arm 24.

The empty spools or tubes 30 on which the yarn bobbins 21 are subsequently to be formed are supplied from a reserve contained in a hopper 102 (as shown in Figures 1,2 and 11). The bottom portion of the hopper communicates with an elbowed upward-transfer guide duct 103, the top opening of which is surmounted by a spool-gripping device generally designated by the reference 105.

This device comprises an elbowed lever 106 (shown in Figure 9), said lever being pivotally mounted at its vertex on a horizontal pin 107 carried by the carriage 1. One of the arms of said lever, namely the arm 106A, is subjected to the action of a cam 109 fixed on the camshaft 59. The other arm 1 06B of the lever 106 carries a pair of tongs or tong unit 112 for gripping spools 101.Thetong unit 112hastwo jaws 113,114 which are pivotally mounted on the end of the arm 106B by means of a pin 115. The two jaws 113,114 are urged elastically towards each other by a spring 116 (see also Figure 11), the two ends of which are attached respectively to the ends of two extensions 117,118 of said jaws.A jaw-opening device comprises an electromagnet 112 carried by the arm 106the moving armature of said magnet being pivotally attached to one end of two link-arms 122, 123, the other end of which is pivotally attached to the end of the corresponding jaw extension 117 or 118.

When the tong unit 112 is in the spool-gripping position as shown in Figures 9 and 11, an electric contact 127 carried by the carriage 1 is in the active position. Another electric contact 128 carried by the tong unit is in the active position when a spool is not present between the arms of the tong unit.

Below the bottom orifice of the hopper 102, a sliding push-plate unit 131 actuated by an electromagnet 132 has the function of thrusting the spools 30 into the guide duct 103. A vertical shutter 135 subjected to the action of an electromagnet 136 temporarily retains the last spool 30A after this latter has been pushed forward in order to permit the following spool 30B to drop from the lower portion of the hopper 102 into the push-plate unit 131 while this latter performs a movement of withdrawal.

Within the interior of the suction nozzle 51 (shown in Figure 10), a knife-blade 141 actuated by an electromagnet 142 has the intended function of cutting against an anvil 143 that portion of yarn 22 which is located within the interior of said nozzle.

All the electromagnets mentioned in the foregoing are controlled by means of the electric programmer 38 which is mounted on the carriage 1.

The operation of the complete assembly takes place as follows: The carriage 1 (shown in Figures 1 and 2) moves along the rail 1 under the action of the runner-wheel 3 which is driven in rotation by the motor 32, electric current being supplied to the motor under the control of the electric programmer 38, with the result that said carriage passes successively in front of all the spinning stations 7 of the machine.

When the diameter of a yarn bobbin 21 attains the desired predetermined value, the photoelectric cell 42 or the feeler 43 carried by the carriage 1 emits a signal which initiates the automatic process of doffing of said bobbin and replacement of this latter by an empty spool. On the one hand, said signal has the effect of cutting-off the supply of current to the electric motor 32, with the result that the carriage 1 stops in front of the spinning station 7 in which the bobbin is full. On the other hand, the signal has the effect of energizing an electromagnet for causing engagement of the locking-bolt 46 carried by the carriage within the bolt clasp which is attached to the rail 3. In consequence, the carriage is maintained in a perfectly stationary and accurate work position with respect to the spinning station.

The electric programmer 38 initiates the supply of the electric motor 39, one function of which is to drive the cam 56 (as also shown in Figure 4). In consequence, the suction nozzle 51 carries out a pivotal movement on the pin 52 in the direction of the arrow f3 and its orifice comes into position above the level of the delivery roller 12. The cam 58 which is driven at the same time as the cam 56 causes a pivotal displacement of the arm 53 (shown in Figure 3) in the direction of the arrow f4. This causes a forward displacement of the suction nozzle 51,the orifice of which is now located against the yarn 22 (as shown in Figure 12).The programmer 38 cuts-off the supply of current to the electromagnet 73 (shown in Figure 5); the spring 71 causes an abrupt pivotal displacement of the curved thread-cutting blade 66 in the direction of the arrow f1,with the result that the yarn 22 is cut immediately above the delivery roller 12 while at the same time, the hook 67 catches hold of that portion of yarn which is connected to the spinning unit 11 and which is subjected to the partial vacuum prevailing within the suction nozzle 51 (shown in Figure 6); this portion of yarn is thus guided within the right-hand portion of the nozzle in Figure 6 (see also Figure 13). The yarn 22 is drawn from the spinning unit 11 by the delivery roller 12 and is sucked into the nozzle 51 as a result of the partial vacuum prevailing within this latter.

The camshaft 59 also drives the cam 83 (Figures 2, 7 and 8) which causes pivotal displacement of the bell-crank lever 85 in the direction of the arrows5.

This causes lifting of the extension 24A of the arm 24 (Figure 13) and consequently results in lifting of the bobbin 21 away from contact with the winding roller 17. The electric programmer 38 causes energization of the electromagnet 87 (Figure 8); this latter thrusts back the arm 85 which in turn thrusts back the extension 24A of the arm 24 in the direction of the arrow f2. The arm 24 moves away from the arm 23 (as shown in Figure 8A), with the result that the spool is no longer retained since the length of this latter is smaller than the present spacing of the two arms 23, 24. At the same time, the suction nozzle 51 continues to move in the upward direction (Figure 14) under the action of the cam 56 and pushes the full bobbin 21 onto the inclined plane 28 (shown in Figure 1).As indicated at 29, said bobbin then rolls down said inclined plane towards a discharge conveyor. The suction nozzle moves further in the upward direction under the action of the cam 56 (shown in Figure 4) and advances within the machine under the action of the cam 58 (Figure 3) towards the position shown in Figure 14 and beyond this point to the position shown in Figure 15, that is to say distinctly above the bobbin-supporting arms 23,24 and within the interior of the machine. In the meantime, the yarn 22 continues to be sucked into the interior of the nozzle 51, with the result that this latter draws the yarn upwards and over the winding roller 17.

The electric programmer 38 releases the electromagnet 122 (Figure 9), with the result that the spring 116 causes the tong unit 112 to close abruptly on the empty spool 30 (Figure 11) which is located at the top of the guide duct 103. The camshaft 59 which continues to rotate drives the cam 109 (Figure 9) which causes the elbowed lever 106 to pivot in the direction of the arrow f6 in such a manner as to ensure that the empty spool aforementioned comes into position in front of the yarn 22 between the pivot-pins 27,28 (Figures 2 and 15) of the two bobbin-supporting arms 23, 24. The electric programmer 38 releases the electromagnet 87 (Figure 8) and the arm 24 moves towards the arm 23, with the result that the spool is now centered on the two pivot-pins 27,28 whilst the electromagnet 122 (Figure 9) is energized by the programmer so as to initiate opening of the tong unit 112 and to permit this latter to disengage from the spool which it has just placed in position. Continuation of the movement of rotation of the cam 109 ensures pivotal displacement of the double-arm lever 106 in the direction opposite to the arrow f6 (Figure 9) in order to cause withdrawal of the tong unit 112 into the interior of the carriage 1.

The camshaft 59 continues to rotate and the cam 83 now causes a pivotal displacement of the doublearm lever 85 (Figure 7) in the direction opposite to the arrow f5. The two arms 23, 24 consequently return downwards so as to bring the spool 30 to rest on the winding roller 17 (shown in Figure 16), the movement of rotation of which has not been interrupted for doffing of the full bobbin and replacement by an empty spool. The yarn 22 is held tightly between the winding roller 17 which rotates and the spool which rests on said roller, with the result that winding of the yarn begins and then takes place in the normal manner.

The programmer initiates the energization of the electromagnet 142 (Figure 10) which actuates the knife-blade 141 for cutting the yarn 22 against the anvil 143 within the interior of the suction nozzle 51.

The choice of the moment at which said knife-blade is actuated makes it possible to adjust the length of the yarn reserve 22A (Figure 16) which forms on the spool 30 during rotation of this latter against the winding roller 17 as said yarn is discharged from the suction nozzle since the opening of this latter is still located in front of said spool. Under the action of the cams 58 and 56 (shown in Figure 2), the suction nozzle 51 withdraws and returns downwards within the carriage 1.

The cycle ends by placing an empty spool in the tong unit. When the electric contact 127 (Figure 11) emits a signal to indicate that the tong unit 112 is in the stand-by position within the carriage and when the electric contact 128 emits a signal to indicate the absence of a spool within the tong unit, a suitable electric circuit energizes the electromagnet 132. The sliding push-plate unit 131 consequently advances in the direction of the arrows7 and causes upward displacement of all the spools which are present within the guide duct 103, with the result that the top spool engages within the tong unit which has been positioned immediately above this latter. The electromagnet 122 causes the tong unit to close on the spool.The shutter 135 moves downwards under the action of the electromagnet 136 in order to prevent the spools 30 from returning into the guide duct 103 while the push-plate unit 131 moves back to its initial position shown in Figure 11 and while the spool 30B located in the bottom opening of the hopper 102 falls into said push-plate unit, whereupon the shutter 135 returns upwards. The cycle of doffing a full bobbin and positioning of an empty spool has then been compieted.

The locking-bolt 46 withdraws from the bolt clasp 47 (Figure 1); the electric drive motor 37 starts up again and drives the carriage 1 for seeking a fresh bobbin which has a sufficient diameter to be doffed.

In the embodiment which has just been described, it has been assumed that the partial vacuum within the suction nozzle 51 was produced by a fan 63 mounted on the carriage 1. In an alternative arrangement, however, the partial vacuum could be produced by a fan mounted on an auxiliary carriage which is coupled to the carriage 1 or alternatively by a vacuum duct arranged alongside the machine.

In another alternative form of construction, it would be possible to make use of the device for starting the winding process with formation of a yarn reserve as described in French patent Application No 7900718 filed by the present Applicant on January 12th, 1979 and comprising a stationary suction nozzle and a stationary hook having a special configuration at each yarn-winding station. However, in the device according to the prior patent Application just cited, an operator has to place the yarn by hand on the suction nozzle and on the hook in order to re-sta rt winding of the yarn with formation of a yarn reserve.In the device according to the present Application, however, the adoption of the prior system in question would entail the need to add a suction nozzle and a special hook at each winding station and to provide the carriage with means adapted to replace the hand of the operator for placing the yarn on the nozzle and on the hook.

A safety system comprising a feeler 6 (shown in Figure 1) and a special hook 9 will now be described.

The feeler 6 is intended to check the presence and tension of the portion of yarn 22 located between the delivery roller 12 and the winding roller 17. Said feeler is pivotally mounted on the carriage 1 by means of a vertical pin 6A (as also shown in Figure 17) and is urged towards the path of the yarn 22 by a spiral spring 6B.

The special hook 9 is intended to cooperate with the portion of yarn 22 which is located between the spinning unit 11 and the delivery roller 12. Said hook is also pivotally mounted on the carriage 1 by means of a vertical pin 9A (see also Figure 18) and is urged elastically by a spiral spring 9B against a stop 9C also carried by the carriage 1. Said hook terminates in an inclined portion 9D located against the normal path of the yarn 22 when the carriage 1 is stopped in front of the spinning station considered. On said inclined end portion of the hook 9 is pivotally mounted a pallet 15 which is mounted on a pin 16 and returned elastically by a spiral spring 18 against a stop 19 carried by the hook 9. The pallet 15 can be locked in position against the stop 19 by the moving armature or core of an electromagnet 20 which is also carried by the hook 9.When the core of said electromagnet has withdrawn as shown in Figure 19, the pallet 15 is permitted to carry out a pivotal movement in opposition to the force of its restoring spring 18.

When the pallet 15 takes up its stand-by position shown in Figure 18 or in other words against the stop 19, said pallet forms with the inclined end portion 9D of the hook a kind of open V-shaped pair of pincers which grips the yarn 22. Finally, when the hook 9 moves away from its stop 9C, it produces action on an electric microswitch 10 carried by the carriage 1 (Figure 1).

The operation of this safety system is as follows: If the carriage 1 detects a full bobbin 21 at any point of its travel and if the yarn is present between the spinning unit and the delivery roller 12, said yarn is caught in the "V" formed at the end of the hook 9 and produces a pivotal displacement of this latter in opposition to its restoring spring 9B, thus moving said hook away from the stop 9C and causing it at the same time to actuate the microswitch 10. Said microswitch then conditions the circuit which controls the carriage drive motor 32 so as to stop the carriage and permit doffing of the full bobbin under the conditions which have already been explained in detail in the foregoing.When the doffing cycle is completed, the feeler 6 (shown in Figures 1 and 17) determines whether the yarn is present and correctly stretched between the delivery roller 12 and the winding roller 17. Two cases can then arise. In a first case, when the carriage resumes its movement, the feeler 6 confirms the presence of the yarn at this point by the fact that it is being slightly displaced by the yarn, and immediately actuates a microswitch (not shown) which is placed in a supply circuit of the electromagnet 10 (Figure 19). In consequence, the core of said electromagnet is withdrawn by attraction and enables the yarn to slide along the inclined end portion of the hook 9 while thrusting-back the pallet 15 which undergoes a pivotal displacement in opposition to the force of its restoring spring 18.As soon as the yarn has moved away from the hook 9 and the pallet 15, this latter is returned against the stop 19 by the restoring spring 18. In the second case, if the yarn is not present at the point considered when the carriage resumes its movement, said yarn cannot cause any displacement of the feeler and the supply microswitch of the electromagnet 10 is therefore not actuated. The pallet 15 is maintained in the locked position on the hook 9 against the stop 19 by the core of the electromagnet.

The yarn 22 therefore remains trapped within the "V" formed by the hook and the pallet but is pulled away as soon as the next movement of the carriage takes place.

Finally, if there is no yarn between the spinning unit 11 and the delivery roller 12, it cannot retain the hook 9 which is displaced by the carriage 1, with the result that the microswitch 10 is not actuated and the supply circuit of the carriage drive motor is not cut-off. The carriage then continues along its path of travel without stopping and does not perform a bobbin-doffing operation, in which case it will be necessary to carry out preliminary piecing of the yarn.

Claims (12)

1. An automatic device for doffing bobbins of yarn and replacing the said bobbins by empty spools on a machine for forming cylindrical or conical bobbins such as a spinning frame, a winding frame or a finisher, for example, in which each yarnwinding unit comprises a winding roller, a spool applied against the said roller being guided between two arms which are capable of pivoting on a horizontal shaft under the action of gravity and of opening-out to a slight extent in orderto permit doffing of a full bobbin and replacement of the said bobbin by an empty spool, characterized in that the said device comprises a carriage so arranged as to move along a rail having a configuration which enables the said carriage to pass successively in front of all the yarn-winding units of the machine and to travel around the entire machine, the said carriage being in turn provided with the following combination of means: a drive motor for propelling the carriage along the rail so that the said carriage always travels in the same direction around the machine, means for detecting a full bobbin within a winding unit as the carriage passes in front of the said unit, means for locking the carriage in front of the said winding unit in response to a signal emitted by the said means for detecting a full bobbin, means for lifting the full-bobbin guiding arms and for allowing the said arms to return downwards with an empty spool until the said spool rests on the yarn-winding roller, means for cutting the yarn between the delivery roller and the bobbin, means for opening-out the bobbin-guiding arms in order to release the said bobbin and for closing the said arms against an empty spool, an empty-spool magazine, means for taking an empty spool from the magazine and placing the said spool between the guiding arms aforesaid, the machine being further provided with means for retaining the end of that portion of yarn which is connected to the delivery roller, the retained portion of yarn being located in front of the delivery and winding rollers but behind the empty spool, and the carriage being further provided with a program mer for controlling all the means aforesaid.

2. A device in accordance with claim 1, characte rized in that the means for retaining the end of the portion or yarn connected to the delivery roller are constituted by a suction nozzle.

3. A device in accordance with claim 2, characte rized in that the suction nozzle is carried by the carriage and subjected to the action of a mechanism for producing up-and-down motion as well as back ward and forward motion of the said nozzle.

4. A device in accordance with claim 3, characte rized in that the suction nozzle is pivotally attached to a lever which is in turn pivotally mounted on the carriage and the nozzle-actuating mechanism com prises cams controlled by the programmer in order to produce action on the said lever.

5. A device in accordance with claim 3, characte rized in that the means for cutting the yarn between the delivery roller and the bobbin are constituted by a cutting blade mounted within the suction nozzle and subjected to the action of cutting control means connected to the programmer.

6. A device in accordance with claim 1, characte rized in that the means for taking an empty spool from the magazine and placing the said spool between the guiding arms are constituted by a tong unit having jaws actuated by an electromagnet, the said tong unit being carried by a pivoting arm subjected to the action of a cam, the said electro magnet and the said cam being connected to the programmer.

7. A device in accordance with claim 3, characte rized in that the suction nozzle is connected to a suction fan carried by the carriage.

8. A device in accordance with claim 1, characte rized in that it comprises means for cutting the reserve yarn to the desired length.

9. A device in accordance with claim 8, characte rized in that the means for cutting the reserve yarn to the desired length are carried by the suction nozzle.

10. A device in accordance with claim 1, char acterized in that the carriage is provided with a releasable hook adapted to engage on that portion of yarn which is located between a spinning unit and a corresponding delivery roller as well as with a feeler for detecting the presence of the yarn between the delivery roller and the winding roller, the hook being intended to control a contact for stopping the carriage drive motor and the feeler being intended to control a contact which supplies current to an electromagnet for releasing the said hook.

11. A device in accordance with any one of claims 3 to 10, characterized in that the suction nozzle actuating mechanism subjects the nozzle to a movement such that said nozzle itself pushes the full bobbin released from the arms towards a full-bobbin discharge element.

12. An automatic device for doffing yarn bobbins and replacing the said bobbins by empty spools, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.