Process and device for the pneumatic holding of a yarn

[0001] The present invention relates to a process according to the introductory clause of claim 1 as well to a device to carry out this process.

[0002] In textile machines, in particular in spinning machines such as open-end spinning machine, it is customary to hold a yarn by means of suction air (DE 23 50 843 A1) to carry out a given work phase. For example, the yarn is cut, merely stored or transferred from one position to another during this work phase. In this process the problem occurs however that the end of the pneumatically held yarn is affected by the air stream and that therefore less than perfect quality is available for the subsequent work steps, so that errors in work or even interruption of the work process may result.

[0003] It is the object of the present invention to create a process and a device by means of which excessive stress on and thereby damage to the yarn end, and thus a disturbance of the work process resulting from such damage, may be avoided.

[0004] This object is attained by the invention through the characteristics of claim 1. Due to the fact that the intensity of the airflow brought to bear upon the yarn is adapted to the current operating conditions, the lowest possible intensity of the air stream can be selected for this purpose so that the yarn is treated with care in the time interval during which it is exposed to the air stream, while the intensity of the air stream yet remains strong enough to carry out its task reliably.

[0005] The term “working conditions” are to be understood in the sense of the present invention to relate to the work phases following the pneumatic holding of the yarn, but also relates to the different yarn characteristics with regard to yarn thickness, fiber material spun into the yarn and yarn structure as well as yarn twist, fiber incorporation, etc.

[0006] The working conditions may be different depending on the textile conditions and/or the operating position. Therefore it is possible, according to an advantageous embodiment of the process according to the invention as outlined in claim 2, to change the intensity of the air stream brought to bear on the yarn end in work phases following each other in time and in adaptation to the task to be accomplished in that case, in order to achieve secure handling of the yarn with the least possible flow intensity in an optimal manner.

[0007] Complementing or alternatively to an adaptation of the flow intensity to different work phases, it is an advantage to adapt the air stream acting upon the yarn end to the character of the yarn, according to claim 3. The “character of the yarn” in this case should be understood to be the yarn thickness, the fiber material spun into the yarn, the twist of the yarn or its structure, etc., which may show considerable differences, depending on the spinning process used.

[0008] According to the invention the air stream for the reception of a yarn set at a high intensity according to claim 4, since the task to be accomplished as a rule consists in releasing the yarn from the influence zone of another element in which it is held by that element. In addition the air stream does not necessarily act upon the end of such a yarn to be accepted, but in some cases upon a middle area of the yarn, so that the latter must be taken up in form of a loop; for this an intensive air stream is useful.

[0009] In a further development according to the invention of the described process, the yarn to be cut is held under tension by an air stream of high intensity according to claim 5, so that the cutting point is accordingly determined very precisely as related to the yarn to be cut.

[0010] If the task consists merely in holding t he yarn after cutting, the intensity is maintained advantageously only until the severed yarn end has been removed according to claim 6, and is then reduced to a value sufficient for the yarn end formed by the cutting process to be held securely on the one hand, while on the other hand it is however exposed to the lowest possible air stream so that the yarn end may not be frayed and may essential preserve its character. In an advantageous further development of the process according to the invention, such a reduction of the air stream intensity is effected according to claim 7, whether or not the yarn was to be cut in the pipe in which it had been held previously.

[0011] According to claim 8 of the invention, in order to reduce the air stream acting upon the yarn, a secondary air stream can be fed to this air stream outside the area in which the yarn is located.

[0012] In another advantageous variation of the described process, and according to claims 9 as well as 10 or 11, the cross-section of aline conveying the yarn and the air stream can be chanted to control the intensity of the air stream acting upon the yarn.

[0013] To carry out the process a device according to claim 12 is used. Thanks to the air control device according to the invention it is possible to control the air stream which can be brought to bear upon the yarn in such manner that it is as weak as possible on the one hand, while on the other hand it is nevertheless so strong that it securely holds the yarn as required by the current operating conditions in an optimal manner.

[0014] The air control device can be designed in different ways. Thus it is possible to design the air control device of the object of the invention in an advantageous manner in accordance with claim 13 or in accordance with the claims 14 and 15 or 15. Beyond this it is possible with the design of the air control device of the invention in accordance with claim 17 to actuate one or several intermediate positions in addition to the two end positions that can also be adjustable. In that case it is advantageous to provide a monitoring device according to claim 18 to adapt the intensity of the airflow to different yarn thicknesses.

[0015] In addition, a yarn severing device can be assigned to the air control device according to claim 19 and, if applicable, also claim 20.

[0016] The process and the device according to the invention make it possible in a simple and optimal manner to hold the yarn carefully, whereby the process and the device are based on the realization that in adapting the air stream to different operating conditions it is possible to hold the yarn securely, depending on the prevailing operating conditions, when the intensity of the airflow is strongest possible as well as when it is reduced. This not only results in a careful treatment of the yarn but, depending on the design of the air control device, also in savings in energy, since the air source need provide less air for certain operating conditions than for other operating conditions.

[0017] Examples of embodiments of the invention are explained below through drawings.

[0018]
FIG. 1 shows an open-end spinning station as well as a service unit with an air control device according to the invention, shown in a schematic side view;

[0019]
FIG. 2 shows a cross-section of an air control device according to the invention;

[0020]
FIG. 3 shows a cross-section of a variant of an air control device according to the invention and

[0021]
FIG. 4 shows a diagram of the intensity of the air stream in function of different operating conditions.

[0022] The device according to the invention is explained below through the example of an open-end spinning machine. On this machine FIG. 1 shows a workstation 1 on the left by means of a line of alternating dashes and dots, while a service unit 2 is indicated on the right side of the figure by means of a dash-dot-dot line. Normally an open-end spinning machine has a plurality of identical workstations 1 adjoining each other along which the service unit can be moved.

[0023] The workstation 1 of an open-end spinning machine selected as an example shows only a schematically drawn open-end spinning device 10 which is fed a fiber sliver B during spinning operation. The fiber sliver B is opened in a known manner into individual fibers in the open-end spinning device 10, and these are then incorporated continuously into the end of a yarn (not shown).

[0024] The open-end spinning device 10 is provided with a yarn draw-off pipe 100 through which the spun yarn is drawn off by means of a draw-off device 11 from the open-end spinning device 10. In the direction of yarn draw-off towards the draw-off device 11 a winding device 12 is provided with a winding roller 120 by means of which a bobbin 121 can be driven for the winding of the yarn spun in the open-end spinning device 10. For this purpose the bobbin 121 is mounted so as to be capable of rotation between two bobbin holders 122. By swinging the bobbin holders 122 the bobbin 121 can be lifted off from the bobbin roller.

[0025] The service unit 2 is provided with a yarn take-up device 25 with a suction pipe 250 which is connected to an air source 6 via a suctionline 251 and a connectionline 252. Between the suctionline 251 and the connectionline 252 is a valve 60 by means of which the negative pressure which can be caused to act in the suction pipe 250 can be controlled. The valve 60 is connected for control to a control device 5 by means of a line 55.

[0026] In the embodiment shown the suction pipe 250 has an outlet 253 which extends parallel to the surface line of the bobbin 121 over the entire length of the latter.

[0027] The suction pipe 250 is mounted on a swivel axis 255 so that it can be swiveled by means of a swivel arm 254. The swivel arm is associated with a swivel drive which is connected for control to the control device 5 by means of a control line 51.

[0028] In the embodiment shown, the suction pipe 250 is furthermore assigned to a yarn-severing device 4 with e.g. two blades 40 and 41 interacting in the manner of scissors. The yarn-severing device 4 is provided with a drive (not shown) which is connected for control via a control line 50 to the control device 5.

[0029] A yarn transfer device 20 with a swivel arm drive 200 of a swivel arm 202 with a suction pipe 203 at its end and mounted on a swivel axis 201 is connected for control via an additional control line 52 to the control device 5. This suction pipe 203 is connected via a negative-pressureline 204 to a valve 61 which is connected to the connection line 252 by means of a connection line 205. The valve 61 is connected via a control line 56 to the control device 5.

[0030] By swiveling it, the suction pipe 203 can be presented to a yarn end preparation device 22 fixedly installed in the service unit 2, said yarn end preparation device 22 being connected via an overpressureline 220, a valve 62 and a connection line 221 to the overpressure side of the air source 6. The valve 62 is connected via a control line 57 to the control device 5.

[0031] Another yarn transfer device 23 with a swivel drive 230 and a swivel arm 232 mounted on a swivel axle 231 supports a suction pipe 233 at its free end. This suction pipe is connected via a negative-pressureline 234 to a valve 63 which in turn is connected via a connection line 235 to the connection line 252. The valve 63 is connected via a control line 58 to the control device 5 with which the swivel drive 230 is also connected for control via a control line 580.

[0032] The valves 60, 61, 62 and 63 thus assume in turn one after the other the function of an air control device 9 as explained below.

[0033] An auxiliary drive 21 of the bobbin 121 is furthermore connected via a first control line 53 with its swivel drive 210 to the control device 5. The swivel drive 210 is assigned to a swivel arm 212 mounted on a swivel axle 211, said swivel arm 212 supporting on its free end an auxiliary drive roller 213 driven in a conventional manner. This auxiliary drive roller 213 can be presented to the bobbin 121 when the latter is lifted off from the winding roller 120 in order to drive the bobbin 121 in a known manner during a yarn search or for renewed winding up of a pieced yarn. To control this drive of the auxiliary drive roller 213, the auxiliary drive 21 is connected via a second control line 59 to the control device 5.

[0034] The structure of the service unit 2 has been described above only to the extent absolutely necessary to understand the object of the invention. It goes without saying that the service unit 2 contains in addition, in a known manner, a plurality of other devices and aggregates not shown here, as well as lines etc. which are however of no interest here.

[0035] The control device 5 is connected via a control line 540 to a higher-order control device 54 which controls and monitors the aggregate and devices of the open-end spinning machine and in particular of their workstations 1 (see control line 541). The control device 5 and/or its higher-order control device 54 are programmed in such manner (by adjustment or by means of a suitably designed software) that it brings the the air control device 9 (valves 60, 61, 63 and 63) in timely sequence into the necessary position to control the intensity of the air stream to be brought to bear on the yarn F.

[0036] The operation of the device the structure of which has been described above shall be explained below with the help of FIGS. 1 and 4. On its ordinate, FIG. 4 shows the intensity of the air stream L and on its abscissa (time axis t) different work phases I, II, III, IV, V and VI, during which the yarn F is located within the yarn take-up device 25 which is chosen here to stand for other yarn take-up devices (e.g. 24) or yarn transfer devices (e.g. 20, 23), where the control of the air intensity is effected in similar manner.

[0037] For the description below of the device whose structure is described above it shall be assumed that breakage of the drawn-off yarn has occurred at the shown work station 1 and that the spinning process has been interrupted as a result. At the same time the feeding of the fiber sliver B to the open-end spinning device 10 is interrupted. Furthermore, the bobbin 121 is lifted from the winding roller 120 by swiveling the bobbin holders 122 and is thereby stopped.

[0038] When the service unit 2 reaches the affected workstation 1 and stops there on its patrol along the open-end spinning machine or as a result of a call-up signal normally triggered in case of a yarn breakage, the piecing process is initiated. For this the auxiliary drive roller 213, controlled by the control device 5 (first control line 53) is brought to bear upon the bobbin 121 which has been lifted away from the winding roller 120. The auxiliary drive roller 213 is now driven in such manner (second control line 59) that the bobbin 121 rotates in counterclockwise direction as shown in the drawing of FIG. 1.

[0039] Simultaneously with the presentation of the auxiliary drive roller 213 to the bobbin 121, the swivel arm 254 with the suction pipe 250 under control by the control device 5 (control line 51) is swiveled towards the bobbin 121 that has been lifted away from the winding roller 120 (see the positions 254′, 250′ of the swivel arm 254 and of the suction pipe 250 whose outlet 253 now assumes the yarn receiving position 253′, these position s being indicated by broken lines) and a negative pressure is produced in the suction pipe 250 through actuation of the valve 60 (control line 55).

[0040] When the bobbin 121 is now driven by the auxiliary drive roller 213 in a counterclockwise direction, the yarn end E located on the bobbin surface reaches the area of the outlet 253 which is presented to the bobbin 121 (see yarn receiving position 253′) of the suction pipe 250 and is sucked into it due to the negative pressure prevailing in this suction pipe 250.

[0041] Since the yarn end E has been “rolled into” the windings of the yarn wound on the bobbin 121 to a certain degree by the rotation of the bobbin 121 between the moment at which the yarn breakage has occurred and the lifting of the bobbin 121 from the winding roller 120 and the stopping and reaching of the stopped position of the bobbin 121, the yarn end E must first be disengaged from these windings on the bobbin 121. For this reason the valve 60 between the suctionline 251 and the connection line 252 is adjusted before the take-up of the yarn F (control line 55) so that a suction air stream of higher intensity flows in the suction pipe 250 and thereby also at its outlet 253 (see flow intensity La in FIG. 4; phase I: yarn take-up). This strong suction airflow seizes the yarn end E and pulls it further into the suction pipe 250. At the same time, due to the rotation of the bobbin 121 imparted to it by the auxiliary drive roller 213, an ever greater length of the yarn F comes within the zone of influence of this air stream L sucked into the suction pipe 250 and is carried off by it.

[0042] When the suction pipe 250 has take up securely and in sufficient length the yarn F unwound from the bobbin 121, the 254 (control line 51) is swiveled so that the suction pipe 250 moves with its outlet 253 away from the bobbin 121 (Phase II: swiveling of the yarn take-up device 25). When this swiveling of the yarn take-up device 25 has caused the yarn F to be deflected more at the outlet 253 of the suction pipe 250, the friction or retention force acting upon the yarn F is so great that the intensity of the air stream L can be lowered if the circumferential speed of the bobbin 121 substantially matches the swiveling speed of the yarn take-up device 25 (see flow intensity Lb in phase III: continued swiveling of the yarn take-up device 25) Since the yarn F has not yet been shortened at this point in time by the yarn-severing device 4, the reduction of the flow intensity can be dispensed with during this phase III (see flow intensity La1 in phase III, indicated by broken lines).

[0043] Finally the yarn take-up device 25 assumes the yarn transfer position indicated in FIG. 1 by a solid line, in which the yarn F is released at a given time for further handling, and is later transferred to the yarn transfer device 20. When this yarn transfer position has been reached, the drive of the auxiliary drive roller 213 and thereby also the bobbin 121 is stopped (control line 59).

[0044] At a point in time coordinated with the piecing process, the yarn-severing device 4 (control line 50) is actuated by the control device 5 so that the blades 40 and 41 execute a movement relative to each other and sever the yarn F located between them (phase IV: yarn severing process and removal of the severed yarn end). For this severing of the yarn F, the latter should assume as stretched a position as possible within the suction pipe 250 so that the length of the yarn F extending from the coil 121 to the yarn-severing device 4 may be defined exactly. For this reason the negative pressure in the area of the suction pipe 250 has as before a high airflow intensity La in that the airflow intensity Lb of the air stream L holding the yarn F and which has been reduced during the phase III is increased by adjusting the valve 60 (control line 55) or, in case that this high intensity had been maintained as before during phase III (airflow intensity La1), continues to be held at this high suction level. Following the severing and removal of the yarn end E the intensity of the air stream L is reduced, this being effected through appropriate actuation of the valve 60 (control line 55) (Phase V: holding of the shortened yarn end). In this manner the yarn F held in the suction pipe 250 is no longer exposed to an aggressive air stream. The intensity of the airflow is lowered as far as possible (flow intensity Lb) without affecting the holding of the yarn F and can, among other things, also assume a different value than during phase III. The yarn F which is held in this manner as before securely by the prevailing negative pressure and the suction air stream flowing through the suction pipe 250 is thus held in a careful manner so that the free yarn end E is not untwisted thanks to this lowered flow intensity Lb of the air stream L but so that its former structure and twist is maintained constant.

[0045] At the latest when the yarn F has been shortened to a predetermined length by severing its yarn end E, the swivel drive 200 of the yarn transfer device 20 is triggered by the control device 5 via the control line 52 in such manner that it reaches the yarn take-up position indicated in FIG. 1 by a full line. By partial or complete closing of the valve 60 (control line 55) the intensity of the air stream L is further reduced, if necessary down to a value of zero (flow intensity L0) and the yarn F which had been held until then by the suction pipe 250 is released (phase VI: release of the yarn). Simultaneously with the closing of valve 60, the valve 61 (control line 56) is opened so that a suction air stream of high intensity flows in the suction pipe 203, causing a yarn F released from the suction pipe 250 to be sucked into the suction pipe 203. The work phases and flow intensities relating to the yarn transfer device 23 are not shown in FIG. 4, as already indicated.

[0046] The suction pipe 203 is brought into its yarn transfer position through renewed actuation of the swivel drive 200 (control line 52) (see positions 202′ and 203′ of the swivel arm 202 and of the suction pipe 203 indicated by broken lines) in which the outlet of the suction pipe 203 is located, across from the outlet of the yarn end preparation device 22.

[0047] The yarn end preparation device 22 is connected to an overpressureline 220 which lets out into the yarn end preparation device 22 in form of an injector (not shown) in such manner that a sucking action is produced at the outlet of the yarn end preparation device 22 towards the suction pipe 203. When the suction air stream in the suction pipe 203 is now taken out of action by closing the valve 61 (control line 56) and an air stream flowing into the yarn end preparation device 22 is produced at the same time through actuation of valve 62, the yarn F released from the suction pipe 203 will follow this air stream and will enter the yarn end preparation device 22. The compressed-air stream which is introduced with great intensity and possibly with tangential orientation components in form of one or several injector openings (not shown) into the yarn end preparation device 22 acts in a known manner on the yarn end E to thin it out in the desired manner for subsequent piecing. When this has been accomplished—as can be determined by time control or can be monitored optically—the intensity of the air stream acting upon the yarn end E is reduced for the remainder of the time during which the yam end E is still held by the yarn end preparation device 22 through actuation of the valve 62 (control line 57). Finally the suction pipe 233 of the yarn transfer device 23 is presented to the outlet of the yarn end preparation device 22 by the control device 5 through actuation of the swivel drive 230 (control line 580), and by opening valve 63 (control line 58 a negative pressure is produce din the suction pipe 233. At the same time intensity of the air stream L acting upon the yarn end F is lowered considerably or eradicated completely through extensive or complete closing of the valve 62 (control line 57), so that the yarn F is released and thus wanders into the suction pipe 233.

[0048] The suction pipe 233 is now brought into its yarn transfer position indicated by broken lines by actuating the swivel drive 230 (control line 580) (see positions 232′ and 233′ of the swivel arm 232 and of the suction pipe 233).

[0049] A negative pressure required for the transportation of the fibers which have been opened in a known manner from the forward end of the fiber sliver B presented to the spinning device 10 is produced in the spinning device 10. This negative pressure takes effect as far as the outermost outlet of the yarn draw-off pipe 100 so that the free yarn end E of the yarn F held by the suction pipe 233 comes under the influence of this suction air stream flowing into the yarn draw-off pipe 100. The valve 63 is then closed (control line 58) so that the suction pipe 233 releases the yarn F. At the same time a predetermined yarn length is fed back in one or several steps in a usual and therefore not shown manner in the direction of the yarn draw-off pipe 100 and is now sucked through the yarn draw-off pipe 100 into the spinning device 10 where the actual piecing takes place in the known manner.

[0050] The yarn F which is fed back into the spinning device 10 can be delivered by the bobbin 121 in that the latter is again driven in back-feeding direction by the auxiliary drive roller 213. The yarn length required for piecing can however be formed in form of a yarn reserve already at a earlier point in time from the yarn length delivered by the coil 121 into the suction pipe 250, this yarn reserve being released at the proper time for the piecing back-feeding though the yarn draw-off pipe 100 into the spinning device 10. Such a yarn reserve can also be formed during the swiveling motion of the suction pipe 203 or 233 from its position indicated in FIG. 1 by a full line into its position 203′ or 233′ indicated by a broken line.

[0051] Following piecing, when all the elements of the service unit 2 required for piecing have again assumed their starting position, the service unit 2 leaves the serviced workstation 1 and is again available for service at other workstations 1.

[0052] The process and the device can have many variants within the scope of the present invention, in particular by replacing individual characteristics with their equivalents or by other combinations of these characteristics or their equivalents. Thus the work station 1 where the described process as well as the described device find their application need not a part of an open-end spinning device 10; this process and this device can rather be used on any textile machine or device in which a yarn is to be handled, be it for its transportation from one position into another (see the suction pipes 250, 203 and 233 in the described example) or be it for improved treatment in combination with a transportation of the yarn F from one position into another (see yarn take-up position and yarn transfer position of the suction pipe 250) or without such a yarn transportation (see yarn end preparation device 22).

[0053] The pipe receiving the yarn F also need not have an enlarged or widened outlet 253 if this pipe does not have the task of taking up the yarn F from the bobbin 121 like the suction pipe 250. This becomes clear through the above example of the suction pipes 203 and 233 where the yarn F is conveyed to the respective outlets of the suction pipes 203 or 233.

[0054] The pipe receiving the yarn F may also be a pipe through which a yarn F provided for piecing which is not unwound from the bobbin 121 is transported from its end away from the outlet in the direction of the outlet which in this case also need not have a greater diameter, where the yarn F is in turn grasped by a grasper or similar device and is conveyed to the yarn draw-off pipe 100.

[0055] The control of the intensity or speed of the airflow is effected according to the above description by corresponding adjustment of the valve 60, 61, 62 or 63. it is however also possible to adjust the intensity of the airflow by means of a central control of the air source 6 since, as the above description shows, the yarn F reaches the valves 60, 61, 62, 63, one after the other in time, whereby these valves 60, 61, 62, 63 merely have the task of switching the air stream on or off in the required zone.

[0056] Depending on whether the valves 60, 61, 62, 63 or the air source 6 control the intensity of the airflow, these valves 60, 61, 62, 63 or this air source 6 constitute the air control device 9 for the air stream L acting upon the yarn.

[0057] If only one air source 6 was mentioned above, without indication of whether it supplies overpressure or negative pressure, this is because this air source 6 serves as negative pressure source or as overpressure source, depending on the connection of the connecting line 252, 205, 206 or 235 etc; it goes without saying that when either negative pressure or overpressure are needed, a negative-pressure source as well as an overpressure source can be provided as autonomous air sources, i.e. independent of each other, instead of the shown combined compressed-air source 6.

[0058] It is also possible to assign the yarn end preparation device 22, by means of which the yarn end E is imparted an especially suitable form for piecing by untwisting or fraying and which is located between the outlet 253 and the yarn-severing device 4 in that case, can be assigned to the suction pipe 250 with the yarn-severing device 4.

[0059] Depending on the design and task of the pipe holding the yarn F, a yarn severing device 4 can be assigned to it functionally and thereby also to the air control device 9 (valve 60, 61, 62, 63 or air source 6) but this is not obligatory, as appears from the above description. If it is provided, the yarn-severing device 4 can be designed in different ways, e.g. as shown, in form of scissors or as a knife, a grinding roller, etc.

[0060] In a device of this type, e.g. in the spinning device 10 shown in FIG. 1, not every yarn take-up device 24, 25 or yarn transfer device 20, 23 need necessarily serve to receive the yarn F with the assistance of a negative-pressure or overpressure air stream, so that these devices do not absolutely require a suction pipe 203 or 233 etc. It may also perfectly be advantageous if e.g. a suction pipe 203 in which the intensity of the air stream L is controlled in adaptation to the different work phases I to VI interacts with a yarn transfer device 23 which is provided with a controllable holding device, e.g. in form of a pair of rollers (not shown), instead of a suction pipe 233. If the two rollers of such a pair of rollers can be driven as needed in one or the other direction, this pair of rollers can take over or assist the back-feeding of the yarn length required for piecing into the spinning device 10, or the take over or assist the start of draw-off of the yarn F following successful piecing from the spinning device 10. The yearn length required for the backfeeding to the spinning device 10 can here be released by suitable reverse rotation of the bobbin 121 by means of the auxiliary drive roller 213.

[0061] According to FIG. 1 a valve 60, 61, 62 or 63 located outside of the range of the length range of yarn F is provided for the control of the air stream L acting upon the yarn F or on the yarn end E. FIG. 2 shows in a detail the example of an embodiment of a valve 7 in form of a choke for the control of the intensity of the air stream L acting upon the yarn end E and with the help of which the cross-section of the line receiving the yarn F can be changed, as will be explained in further detail below. The yarn take-up device 24 shown can be in this case the yarn transfer device 20 or 23, the yarn take-up device 25 or also the yarn end preparation device 22, or can be designed as a part thereof

[0062] The yarn take-up device 24 shown contains the previously mentioned valve 7 between a suctionline 240 and a connection line 242 connected to the negative-pressure side of the air source 6. The suctionline 240 and the connection line 242 are essentially aligned with each other and their two ends towards each other end in a housing 70 extending essentially perpendicularly to the longitudinal axes of the suctionline 240 and the connection line 242. The housing 70 receives a ram or piston 71 which is connected via a piston rod 72 (only indicated) to a drive 73 which in turn is connected by means of a control line 730 to the control device 5 (see FIG. 1). The housing 70 is closed by a cover 74 on its side across from the drive 73.

[0063] When the full intensity of the airflow is to act upon the yarn end E, the piston 71 is with its face 710 in the position 710a of the face 710 indicated by a broken line. The air stream can then flow unimpeded through the suction line 240, the housing 70 and the connection line 272 and is thus acts upon the yarn end E with the greatest possible intensity.

[0064] If the intensity of the air stream L brought to bear on the yarn end E is to be reduced for a given work phase I to VI, the piston 71 is pushed to the left through appropriate control, as seen in the drawing of FIG. 2 by the control device 5 (control line 730), so that the cross-section in the area of housing 70 through which the air stream must flow is reduced. This causes the flow speed of air inside the housing 70 accelerate because of the reduction of the cross-section, but it is reduced due to the throttling achieved in the area of the suction line 240, with the result that the airflow now acts only with reduced intensity upon the yarn end E which does not reach as far as into the housing 70 but merely extends into the suction line 240.

[0065] If desired, the valve 7 can at the same time be designed as the yarn-severing device 4, so that this yarn-severing device 4 is an integral part of the air control device 9 constituted by the valve 7. In this case the annular edge 711 between the circumferential surface 712 and the face 710 of the piston 71 is designed as a cutting edge. In addition the longitudinal area 701 of the housing 70 is widened by a distance between the end 241 of the suction line 240 and the end 243 of the connecting line 242, as compared with the area of the housing 70 for the movement of the piston 71, so that an anullar edge 700, also in form of a cutting edge, is produced on the side of t his longitudinal area 701 towards the cover 74. If the drive 73 is actuated once the yarn F has been sucked into the suction pipe 240 by corresponding control while the piston 71 is completely pulled back, and thus with an intensively acting airflow, then the piston 71 moves to the left, relative to the drawing in FIG. 2, until the yarn F is finally severed by the interacting annular edges 700 and 711 (see the position 710b of the face 710 indicated by a dash-dot-dot line). The piston 71 is then withdrawn immediately so that the airflow can again act upon the yarn F. Depending on the intensity of the air stream L that is desired after the severing process, the piston 71 returns here only into the position of face 710 indicated by a continuous line or into the position 710a indicated by a broken line.

[0066] Depending on the desired intensity of the airflow, e.g. in adaptation to different yarn thicknesses, or depending on the type of fiber material being spun, it is of course also possible to provide another end or intermediate position of the piston 71 which is not shown.

[0067] To prevent the yarn F from being temporarily subjected to no airflow at all during the severing process, it is possible, through appropriate design of the inner contour of the housing 70 and/or of the piston 71 to ensure that an airflow is always maintained and acting on the yarn F without taking it out of severing range, even when the yarn-severing device 4 constituted by the annular edges 700 and 711 becomes active.

[0068] As described below, it is possible to achieve a reduction of the airflow intensity also by changing it in a manner other than by reducing the line (suction line 240, housing 70, connection line 242) conveying the air stream L. Thus I is possible to achieve a reduction of the intensity of the air stream L acting upon the yarn end E when the yarn end E extends not only into the suction line 240 but as far as into the longitudinal area 701 of the housing 70, by enlarging the cross-section of the housing 70 in that longitudinal area 701. In that case the piston 71 is not only withdrawn to the position 710a indicated by a broken line in which the face 710 is essentially in prolongation of the inner walls of the suction pipe 240 and of the connection pipe 242 towards the drive 73 in order to reduce the intensity of the air stream L acting upon the yarn end E which extends into the longitudinal area 701 of the housing 70, but beyond this in direction of drive 73 into position 710c, so that a significant enlargement of the cross-section of the housing 70 is achieved. Large enough sizing of the longitudinal area 701 of the housing 70 in the longitudinal fiber direction indicated by axis A in FIG. 2 is naturally required for this.

[0069] Another alternative embodiment of a valve 8 for the control of the intensity of the air stream L acting upon the yam end E is described below through FIG. 3. Here too the suction line 240 of a yarn take-up device 24 as well as the connection lines 242 are shown, whose ends 241 and 243 facing each other leave a distance between them. These ends 240 and 243 are surrounded by a sleeve 80 which can be displaced in longitudinal direction along axis A and which in its shown end position closes the space 81 created by the distance between the ends 241 and 243 radially against the outside. On a portion of its circumference, the sleeve 80 is provided with an opening 82 which can be moved by axial displacement of the sleeve 8 from its shown end position to a position 82a indicated by a broken line in which the space 81 is connected to the atmosphere or environmental air surrounding the sleeve 80.

[0070] As shown in FIG. 3, the yarn F to be held extends with its yarn end E into the suction pipe 240 and does not reach as far as into space 81.

[0071] If an air stream of high intensity is needed for the reception or handling of the yarn F, the space 81 is closed off from the outside by moving the sleeve 80 into the position shown in FIG. 3 by a continuous line, without changing the capacity of the air source. If on the contrary, not such a strong negative pressure is needed to hold the yarn F in a given work phase, the sleeve 80 is moved by the control device 5 into a position in which the space 81 is opened to the desired extent to the air surrounding the valve 8. In this manner an air stream (secondary air stream) flows through the freed opening between the ends 241 and 243 of the suction line 240 and the connection line 242 into the space 81, so that the intensity of the airflow is reduced correspondingly in the area of the suction line 240 in which the yarn end E is located.

[0072] If a greater intensity of the air stream L is again required in the area of the yarn end E, the sleeve 80 is moved back into its starting position.

[0073] So far it has only been stated that the intensity of the negative pressure is modified in the area of yarn end F in adaptation to different work phases I to VI so that it is able to fully play its role on the one hand, but is kept as low as possible so that the yarn end E subjected to the air stream L caused by the negative pressure is held with the greatest care. It addition it must however also be considered that such an adaptation of the air stream intensity L can also be applied to other work conditions in addition to the work phase. For example, a thin yarn F naturally reacts with much greater sensitivity to such an air stream than a thick yarn F. For this reason provisions are made to adapt the intensity of the air stream not only to the different work phases I to VI, but if necessary is maintained at a different level of intensity also in function of the thickness of the held yarn F. This level of the intensity of the air stream L can first be determined empirically and can then be adjusted manually; it is however also possible to provide a sensor in the yarn holding device. Such a sensor (monitoring device 3) is shown in FIG. 1 in connection with the yarn take-up device 25; this monitoring device 3 is connected for control via a control line 30 to the control device 5 and has the task of determining the yarn thickness and transmit it to the control device 5 which adjusts to the full or the reduced intensity of the air stream L in function of this ascertained yarn thickness. For this purpose the air control device 9 (valve 60, 61, 62, 63, 7 or 8) is brought into a corresponding intermediate position or is driven at the corresponding rotational speed (air source 6).

[0074] In FIG. 1 for example, with reference to the above-mentioned phases I to VI, La′ , designates the maximum flow intensity with a thick yarn and La″ designates the maximum flow speed with a thin yarn F, while Lb′ designates the reduced flow intensity with a thick yarn F and Lb″ designates the reduced flow intensity with a thin yarn F. Of course the values for and the relationships between the flow intensities La, La′, La″ on the one hand and the flow intensities Lb, Lb′, Lb″ on the other hand can be selected in function of the prevailing conditions.

[0075] Similarly, an adaptation to the character of the yarn with regard to the type of fiber material spun and/or to the yarn twist can be taken into account in determining the flow intensity of the air stream L. The structure of the yarn F which is different e.g. in a wrap-around yarn than in an open-end yarn or in a yarn F spun on a ring-spinning machine is to be taken into account.

[0076] Depending on the type of textile machine, the workstation 1 can be designed in different ways; thus the work station 1 could be part of a spinning machine, of a winding machine or similar device. Accordingly the service unit 2 would then also be designed differently and could also be an integral component of the work station 1 if necessary.

Process and device for the pneumatic holding of a yarn

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CPC

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