Abstract:
A reel-stick arm for winding yarn with regulated pressure between the reel and its actuation roller, particularly for double-twist twisting frames, comprising automatic means for balancing the effect of weight variation of the reel being formed, means for automatic raising of the reel-stick arm, and automatic means for clamping the arm in the raised position, said raising and clamping means being co-ordinated by interlocking means.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the winding of yarn on reels or packages in textile machines for the preparation of yarn, and in particular relates to a device with a reel-stick arm supporting the rotating tube on which the reel of yarn is formed. 
     FIELD OF THE INVENTION 
     In industrial practice, a solution that has met with considerable success is that of actuating the tube in rotation—with the reel that is formed by winding the yarn on its surface which has the shape of a truncated cone or cylinder—by driving the said tube in rotation with an underlying motor-driven roller on which the reel itself rests, thus enabling winding of the yarn at a constant linear speed that is independent of the size of the reel, which grows as the winding operation proceeds, and dependent only upon the speed of rotation of the said actuating roller. The yarn is wound in turns on the reel and distributed with a to-and-fro motion over its generatrix by a traversing device. 
     BRIEF SUMMARY OF THE INVENTION 
     A problem linked to the winding of yarn of a reel resting on its actuating roller is due to the fact that the reel, as it grows, exerts an ever-increasing weight and applies an ever-increasing pressure on the roller, with consequences on the progress of the operation and on the mechanical and geometrical characteristics of the reel produced. For instance, the reel itself becomes more and more deformed at its point of resting as it grows. As a result, both the tension of the turns of yarn and the density of the wound layer increase. As the pressure exerted varies, the transmissible torque, especially in the speed transients, varies noticeably, and the possibility of mutual friction increases. 
     In order to highlight more clearly the technical problems tackled and solved by the present invention, as well as the characteristics and advantages of the invention with respect to the prior art, the said invention is here described with reference to its application in gathering units for yarn produced on double-twist twisting frames by winding it in reels, even though the device according to the invention may also find application in the entire range of machines for preparing and finishing yarn in which the yarn is wound in reels. Consequently, application of the invention is not at all intended to be limited to twisting frames alone. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a side view illustrating a typical scheme of a gathering unit of a station of a double-twist twisting frame. 
     FIG. 1B is a front view illustrating a typical scheme of a gathering unit of a station of a double-twist twisting frame. 
     FIG. 2A illustrates the reel-stick arm assembly in its configuration with the reel at the start. 
     FIG. 2B illustrates a top view of the reel-stick arm assembly fork. 
     FIG. 2C illustrates a sectional view counter-weighting device. 
     FIG. 3 illustrates the reel-stick arm assembly in its configuration with the reel about to be completed. 
     FIG. 4 illustrates the reel-stick arm assembly in its configuration with the reel raised by intervention or reel completion. 
     FIG. 5 is a sectional view of the reel-stick arm assembly illustrating the components of the raising device. 
    
    
     FIGS. 1A and 1B are, respectively, a side view and a front view illustrating a typical scheme of a gathering unit of a station of a double-twist twisting frame, in which the most significant members are illustrated in order to highlight the technical problem in question. 
     The twisting operation consists, in its main aspects, in joining together two or more threads of yarn, which are already twisted, by means of a further mutual twisting about their axis. Retwisting produces a yarn of a higher quality, greater strength and regularity, and improved appearance and “feel” as compared to the original starting yarn. 
     As in the case of other machines for preparing and finishing yarn, the double-twist twisting frame is made with a plurality of working units set alongside one another along one or two fronts with appurtenances, driving means and control unit that are in common. FIGS. 1A and 1B are, respectively, a side view and a front view illustrating the scheme of the basic parts of the system for gathering the thread in a twisting frame. 
     The supply of yarn is constituted by two threads  1  and  2 , coming from the feed reels located in the underlying cylindrical basket  3 , the said threads  1 ,  2  being inserted in the reeling-off head  4  and twisted in the bottom part of the station, which is not shown in the figure for reasons of simplicity of representation. The double-twisted yarn  6  then returns upwards, where it is gathered. The said double-twisted yarn  6  whirls, and its balloon is controlled first by the internal wall of the containment cylinder  3  and then by the yarn-guiding eyelet  7 . The yarn is recalled by the pull exerted by the top reel that is being wound. 
     Proceeding in the direction of the reel, downstream of the yarn-guiding eyelet  7 , the yarn  6  then encounters a yarn-feeler  10 , an idler wheel or pulley  11 , and the drawing mechanism or tractor  12 . The said tractor consists of two rotating plates or cups set facing one another to form a tortuous groove that engages and pulls the tensioned yarn so as to divide the action of tension between the tractor and the reel. In normal operating conditions, the twisted yarn  6  then passes from the yarn guide  13 , which distributes it over the generatrix of the reel with a driven to-and-fro motion along the guide  14 . 
     The reel  16  of yarn being formed, which recalls and gathers the retwisted yarn  6 , is wound on the base tube  17 , which is also carried by a reel-stick arm  18 , and is driven in rotation by a cylinder or roller  19  rotating at a constant speed. The reel-stick arm consists, in its essential features, of a liftable fork and two jaws which open with respect to one another in order to open and close two centring shafts or supports that block the tube on which the yarn is wound to form the reel. As gathering of the yarn proceeds, the reel  16  rotates resting on the roller  19 , increasing its diameter and decreasing its angular velocity. The reel increases in weight and volume, and the arm  18  lifts up gradually. The reel is exposed to the phenomena described in the preamble of the present description as a result of its variation in size. 
     If the yarn  6  is interrupted either because it breaks or because it runs out, even in the sense that just one of the two feed threads runs out, the yarn-feeler  10  drops, rotating about its shaft, causes the arrest command from the control unit, and activates the alarm for the operator. It must in fact be borne in mind that, in the absence of one of the threads, the surviving thread is considerably weakened in that it is in conditions of untwisting, and hence does not withstand the tensile force and thus breaks. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The characteristics and advantages of the device according to the present invention emerge more evidently from the description of a typical embodiment thereof, which is provided by way of non-limiting example, with reference to FIGS. 2 to  5 . 
     FIGS. 1A and 1B illustrate the scheme of gathering of the yarn in a double-twist twisting frame, to which the reel-stick arm is applied by way of example. FIGS. 2A-C illustrate, instead, the reel-stick arm according to the present invention in its configuration with the reel at the start, with regard to the structure and operation of said arm. FIG. 3 illustrates, instead, the reel-stick arm according to the present invention in its configuration with the reel about to be completed. FIG. 4 illustrates the reel-stick arm according to the present invention in its configuration with the reel raised on account of an intervention or on account of reel completion. FIG. 5 is a sectional view with details of the reel-stick arm illustrating the components of the raising device, the clamping device, and the device for damping the reel-stick arm. 
     FIGS. 2A,  3  and  4  are provided with enlarged details of the main components of the devices for counter-weighting, lifting, clamping, and damping with which the reel-stick arm is provided. 
     FIG. 2A is a side view of the reel-stick arm, and FIG. 2B is a top view thereof. The reel-stick arm is made up of a fork  20  formed by two arms  21  and  22 , one of which—in FIG. 2A the arm  22 —is hinged in  23  and can open and close the fork  20  according to a rotation α for inserting or removing the base tube  17  on which the reel is formed into/from its gripping position between the two centring shafts  24  and  25 . Opening the fork  20  is countered by pulling or tension spring  25 A, which tends to grip the ends of the tube between the two arms. The arm  22  is provided with an extension  22 A which enables the operator to grip it for opening and closing the fork  20 , as well as for raising and lowering the reel—stick arm manually. 
     The base  26  of the fork  20  orthogonal to the arms  21 ,  22  is hinged so as to enable a rotation β about a substantially horizontal pin  28  to raise and lower the reel-stick-arm assembly. The pin  28  is constrained to the fixed structure  31  of the twisting frame. On the opposite side, the base of the fork  26  is provided with a lever arm  32  for the raising device, which will be illustrated in what follows. The base  26  of the fork  20  orthogonal to the arms  21 ,  22  is moreover equipped with a circular sector  33  for the device for clamping the raised reel-stick arm, which is likewise described in what follows. 
     The base  26  of the fork  20  is further provided with counter-weighting means  35  which enable the effect of the increasing weight of the reel to be countered and the pressure between the reel  16  and the roller  19  to be kept within pre-set values. This device is made up of two coaxial hollow pistons  36 ,  37  which slide with respect to one another and contain a compression spring  38 , which tends to move them away from one another. The structure of the two pistons is illustrated in the cross-sectional view of FIG.  2 C. The two pistons  36 ,  37  are respectively provided with ball-and-socket joints  39 ,  40  at their ends, which are constrained with male and female spherical couplings  41 ,  42 , respectively to the fixed structure  31  of the twisting frame and to the base  26  of the fork  20 . The couplings of the pistons are exemplified, in the embodiments shown herein, as ball-and-socket joints, but they could be obtained even with different types of constraint, for example as cylindrical articulated joints. 
     Operation of the counterweighting device  35  is described in what follows. In the configuration of FIG. 2A, the reel wound on the tube still has a small diameter, and the arms  21 ,  22  of the fork are in the relatively lower position. In this configuration, the direction of the axis  44  of the two coaxial pistons passes on the right, i.e., inside the pin  28 . The thrust of the compressed spring  38  inside the pistons thus results in a supplementary weight which causes the reel  16  to weigh against the roller  19 . The thrust of the spring  38  is thus added to the small weight of the reel in the initial phase. As the diameter of the reel  16  increases, the direction of the axis  44  of the pistons  36 ,  37  turns according to the rotation γ about the centre of the ball-and-socket joint  39  and approaches the centre of the pin  28 , thus reducing the arm of the thrust of the spring  38  and the pressure exerted on the roller  19 , until it vanishes when the direction of the axis  44  of said pistons passes through the centre of the pin  28 . 
     When the direction of the axis  44  of the pistons  36 ,  37  has passed through the centre of the pin  28  and moves to the left, i.e., outside the pin  28 , so assuming the configuration of FIG. 3, the thrust of the compressed spring  38  in said pistons thus results in a force that opposes the weight exerted by the reel  16  and reduces the pressure on the roller  19 . From this moment, as the diameter of the reel increases, the direction of the axis  44  of the pistons  36 ,  37  moves further and further away from the centre of the pin  28 , thus increasing the arm of the thrust of the spring  38  and the action of counter-weighting, i.e., the action of reducing the pressure exerted on the roller  19  by the weight itself of the reel that is being completed. 
     The values of the range of pressure that it is intended to apply between the reel and the actuating roller, as well as the value of the diameter of the reel at which the action of the counter-weighting device  35  is reversed, can be adjusted by intervening both on the geometry of the system and on the calibration of the spring  38 . The said adjustment means may intervene advantageously on the position of connection of the ball-and-socket joints  39 ,  40 , for example on the position in which the joint  39  is fixed to the fixed structure, thus varying the diameter of the reel at which reversal of the action of the counter-weighting device  35  occurs. 
     When the reel has reached the desired length, i.e., the pre-set size, the finished reel  16  is removed and replaced by a new tube  17 . In order not to damage winding of the yarn, the reel  16  is made to stop by raising it beforehand from its actuating roller  19 . The procedure is much the same also when an intervention is to be carried out during production of the reel of yarn, for example when twisting is interrupted because the yarn-feeler  10  drops and signals interruption of the yarn  6 . To detach the reel from its roller, there is the automatic lifting member  50 , which consists of a cylindrical piston  51  operated by fluid means, for example pneumatically, that slides in an underlying cylindrical chamber  52 . In the embodiment illustrated in FIGS. 4 and 5, the said pneumatic actuator is a single-acting one, the return into the working position being entrusted to the contrasting action of a compression spring  53  set inside the chamber  52 . Connected to the piston  51  is a vertical stem  54  which carries an engagement member, for example a projecting pin or roller  55 , designed to grip the end of the lever arm  32  set opposite to the fork  20 . With introduction of fluid under pressure by means of the duct  57 , the piston  51  is lowered, so compressing the spring  53  and withdrawing the stem  54  with the roller  55 . In its travel downwards, the said roller intercepts the end of the lever arm  32  and lifts the entire reel-stick-arm assembly, with its reel  16  wound, with a rotation β about the pin  28 . According to a preferred embodiment, opening of the valve and entry of the fluid into the cylindrical chamber  52  is directly interlocked to dropping of the yarn-feeler  10 . 
     The rotation β also involves the circular sector  33 , which is integral with the base  26  of the reel-stick arm and which carries an automatic device  59  for temporary blocking of the reel-stick arm in the raised position, which is illustrated also with reference to the details of FIGS. 2A,  3 ,  4 , and  5 . 
     The circular sector  33  consists of a plate which describes the arc of a circle  60  and which is rendered integral with the base  26  of the fork  20  and rotates with the latter, resting against the contrast surface of a fixed shoulder  61  that is integral with the fixed structure  31  of the twisting frame. At its innermost end, the plate  60  has an appendage  62  having a circular through hole  63  which serves as point of engagement for the terminal ball  64  of the moving element of a device  65  for clamping the reel-stick arm, also this device being integral with the fixed structure  31  of the twisting frame and being subject to the thrust of a spring  66  against the through hole  63  and a spherical seat  67  made in the fixed shoulder  61 . The said clamping is performed when the rotation β first brings the appendage  62  of the plate  60  to be inserted and to displace said ball  64  from its seat  67 , into the position  64 ′ of FIG. 4, as defined by the dashed-and-dotted-line, in such a way that said appendage  62  continues to rotate until its hole  63  comes to correspond with the ball  64  and to enable the ball  64  to be re-inserted into its seat  67 , so gripping the appendage  62  and the plate  60 , thus carrying out temporary clamping of the reel-stick arm in a raised position. Once the reel-stick arm is clamped, the piston  51  and the stem  54  can be lifted up again independently of resetting of the arm itself. 
     Operation of the lifting and clamping members is appropriately provided with means of interlocking and co-ordination, both by controlling lifting interlocked to the dropping of the yarn-feeler  10  and by controlling interruption of lifting of the reel-stick arm when clamping occurs. For instance, for this purpose the sector  33  is equipped with angular-coordinate sensors which enable the control unit of the machine to interrupt introduction of fluid into the chamber  52  in due time, or else the seat  67 , which the terminal ball  64  moves away from or up to, is provided with sensors. 
     The angular value of lifting of the reel-stick arm according to the rotation β at which clamping occurs may be adapted and adjusted, for instance by modifying the mutual position between the plate  60  and the base  26  of the fork  20 . 
     With the reel-stick arm raised, braking and arrest of the reel can be performed without any problems, and likewise the other operations required from the operator, who, when he arrives, finds the arm raised and the reel  16  already separate from the roller  19 . The arm can be reset to cause the reel, or the new tube, to return into contact with the roller  19  after it has raised the stem  54  again, releasing the pressure in the chamber  52  and enabling release of the spring  53 , which brings the piston  51  back up. The arm can then be lowered again by the operator by overcoming the resistance of the spring  66  with the lever  22 A, with a force sufficient to cause the clamping ball  64  to move back from its habitual seat  67 . 
     According to a further improved embodiment of the invention, a device  69  for damping the vibrations or oscillations of the reel-stick arm due to the irregularities of the twisting operation is applied, again on the circular sector  33  that is integral with the base  26  of the fork  20 , or else on the plate  60 . This device consists of a piston  70  which can slide within a chamber  71  that is integral with the fixed structure  31  of the twisting frame and which is pushed at its end  72  by a spring  73  against the plane surface of the plate  60 , compressing it against the fixed shoulder  61 , so as to exert an action of friction and damping of the said stresses which adversely affect the quality of the twisted yarn and the finished reel. According to a preferred embodiment of the invention, the pressure exerted by the spring  73  is appropriately adjusted, for example by a calibration screw, for imparting the desired damping action. 
     The reel-stick arm according to the present invention enables the problems described previously to be overcome both in the course of normal winding of the reel and in the course of interventions in which there are stops, starts, and transient operating conditions. 
     The reel-stick-arm device enables winding of a package as well as any intervention of the operators, safeguarding the quality of the yarn and of the wound package, which, especially in the twisting processes, is required to be of the highest level. 
     The device may moreover be adjusted in such a way as to exert a winding pressure between the reel  16  and the actuation roller  19  within a pre-determined range that is independent of the state of advance of the reel. This enables the preparation of stable reels having uniform and pre-determined densities.