BACKGROUND OF THE INVENTION
This invention concerns an improvement in and to winders for yarn cops, and in particular in and to so-called "parallel winders," with a programmed and controlled yarn tension.
The invention finds a particular application in the field of devices that comprise a winding assembly consisting of a spindle, adapted to support and to impart a rotary motion to a cop whereon the yarn is to be wound, a controlled speed drive means, by which the spindle is driven, a distributing device, adapted to distribute the incoming yarn cyclically across the whole length (or axial dimension) of cop and a swingable arm, carrying a dancer idle pulley, around which the yarn is engaged in a loop in advance of the distributing device, whereby a preset tension, at which the winding is to be carried out, is imparted to the yarn.
As well known, the arm, biased by suitably calibrated spring means, that can be adjusted and controlled according to the progressively increasing diameter of the cop which is being wound, is shifted as a function of the possible differences between the linear feeding speed of the yarn to the winder and the cop-winding speed. The shiftings or swinging motions which the arm undergoes, as a consequence of the changes in the speed and/or in the tension of yarn, are utilized to control the output, and thus the speed, of the motor by which the spindle is driven. Such control may be carried out by different means and preferably--but not necessarily--by acting on an electric circuit that is interlocked with a photocell or preferably a photoresistor, excited by a light source, with the amount of light effective on the photocell or photoresistor being varied in accordance with oscillations of the arm, all as disclosed in my above U.S. patent.
As can be readily appreciated, the most favorable operating conditions, by which the smoothness and evenness of winding are influenced, can be theoretically attained when the arm is kept steadily in a preestablished position, and in particular in that position which corresponds to the middle point of its possible swinging amplitude. Obviously, such requirement cannot be strictly met, owing to the unforeseeable variations which may occur in the tension, feeding and winding conditions. On the other side, notwithstanding the fact that the counterspring means, by which the arm is biased against the yarn tension, are realized in such a manner as to ensure an approximate steadiness of the moment that is applied to the arm, when in a position other than the middle one, it is obviously far from being possible to have such steadiness strictly ensured. Thus, the most favorable conditions are obtained when the device allows, by its operation, to keep the arm within the most narrow possible range of positions surrounding the middle position.
Also further factors preferably are to be borne in mind, to ensure the highest efficiency of equipment. Thus, e.g., the device should return quickly back to its normal operating position, at the end of every possible perturbation. In addition, such theoretically preferable condition should be maintained through the whole winding time, i.e. independently from the progressive increase in the cop diameter. Moreover, the corrective interventions and the return of the arm back in its normal operating position should be sufficiently quick, but also damped, in order to prevent any further oscillation, in particular under resonance or unstability conditions.
To positively avoid any oscillation and perturbation phenomena under the action of small transient changes, it would be preferable to keep the extent of each intervention restricted to small values, thereby to impart a given smoothness to the intervention and to ensure a proportionality of the amount of intervention to the extent of perturbation. On the other side, to stabilize the action of winder and to keep the operating conditions thereof close to the theoretical ones, powerful and quick intervention would be required when any perturbation occurs.
SUMMARY OF THE INVENTION
The object of this invention is to provide a winder, and in particular parallel winders of the considered type, improved in such a manner as to prevent, or at least to strongly reduce, the drawbacks and limitations of heretofore known devices.
In particular, the object of this invention consists in the provision of improved parallel winders, comprising controls and intervention means adapted to meet the above-stated contrasting requirements.
Such purposes are essentially attained, according to the invention, by having a primary system, by which the motor input is controlled and adjusted in relation to the instantaneous position of the arm, associated with a second system, that operates independently from the arm position, and exclusively according to the direction in which the arm is moved under the action of perturbation.
In particular, the invention is carried into practice, by having a control system, preferably--but not necessarily--operating on the basis of changes in the excitation of a photoresistor, depending on the position taken by the arm, associated with a switching system interlocked with the swinging direction of the arm, independently from the position at which the arm starts to swing, and which switching system controls an auxiliary circuit by which an instantaneous and relatively large change in the motor input is ensured, each time the arm is shifted in a direction indicative of a difference, in a predetermined sense, between the linear feeding speed and the yarn-winding peripheral speed.
According to a further feature of the invention for the purpose of a full control of the operating conditions of the winder, advantage is taken of the relatively small cyclic motions which the arm undergoes as effects of the likewise cyclic changes in the distance between the guide pulley (fitted on the arm) and the yarn guide, and caused by the motion of the mechanism.
The switching system is realized in such a manner as to be adapted to intervene within the width or amplitude of the small motions, and thus with the correlated frequency (which, as well known, is reduced with the increase in the cop diameter) while the peripheral speed of winding remains unchanged. Thus, a condition of quick and cyclic interventions is established, which is automatically adapted to the progressive variation in the winding conditions, resulting from the progressive increase in the diameter.
The above and further purposes, objects and features of the invention will be hereinafter disclosed and pointed out, in the course of the following detailed description of a preferred but not restrictive embodiment of the invention, as shown in the accompanying drawing, wherein only the components and structural details which are essential for the invention are represented, while all other prior art components are omitted, or shown diagrammatically.
FIG. 1 is a diagrammatic perspective view of a winder of the considered type, improved according to the invention;
FIG. 2 is a fragmentary side view of the switching device, interlocked with the components by which the arm motions are followed, and
FIG. 3 is a view looking from the right of FIG. 2 and partly sectioned on the plane III-III of FIG. 2.
As shown in FIG. 1, a parallel winder of the considered type comprises a cop 10, driven by a motor M, and whereon the yarn F is wound, the yarn being guided by a dancer pulley 13, carried by an arm 15 that can be swung round an axis 0-0 coinciding with the axis of a shaft 14. The yarn is distributed on the cop 10 by an already known distributing device, of which the yarn guide 11 only is diagrammatically shown, the yarn guide being moved cyclically and alternately in the directions A and B. As a consequence thereof, the distance between the pulley 13 (that is assumed as stationary) and the yarn guide 11 undergoes cyclic changes, which depend on the width of the motion of guide 11 and having a frequency that depends on the angular velocity of the cop.
By means of a suitable spring set, that may comprise e.g. three springs 23, 24 and 31, a force D is applied to pulley 13. Such force D is maintained nearly constant throughout the amplitude X--Y of the admissible oscillations of arm 15, and the tension of the yarn being wound is determined by it. The device may be completed by already known safety means (not shown), such as e.g. limit switches, by which the operation thereof is discontinued when the end positions X and Y are attained by the swinging arm, by means for the calibration and adjustment of the elastic resistances, both initial and depending on the progressive increase in the diameter of cop 10, and so on.
As well known, the swinging motions of arm 15 are caused by the possible differences between the speed Vf at, which the yarn F is fed, and the speed Vr, at which the yarn is wound on the cop 10. Such differences result in a motion in either direction X or Y of the arm. Moreover, small cyclical oscillations x'-- y' are imparted to the arm, due to the aforestated motion of yarn guide 11, pertaining to the distributing mechanism.
The "basic" intervention on the input circuit of motor M, when differences occur between yarn-feeding speed Vf and yarn-winding speed Vr, is preferably performed by a change in the action exerted by a light source 43 on a photoresistor 44, as a consequence of the motion of a light intercepting shield 42, connected with an extension 41 of shaft 14. Such intervention can be advantageously obtained by acting on the control 50 of an already known controlled diode feeder 51, connected across the motor feeding circuit 52.
The control voltage is applied, e.g. through a circuit starting from a terminal 53, connected with a voltage source (not shown), and that comprises, in addition to photoresistor 44, a main switch 54, a possible amplifier 55 and a set of resistances 56, 57 and 58, some of which are of the variable type for the required calibrations and adjustments.
Thus, assuming that the winder is made up of the aforedescribed means and components only, it would operate similarly to prior art winders. The sensitivity, regularity and reliability of both the intervention and control obviously depend on the good operation of the counterspring system, and of different control means and circuits. However, as can be readily appreciated, such conditions cannot be better than the presently attained limits, and are inherently subject to all drawbacks and restrictions initially mentioned.
By the improvement according to this invention, the above described control system (or any other equivalent one) is associated with a second system that operates as a result of the direction of arm swinging motions, independently of the starting point of same motions. This system comprises a switching means I, by which wide variations are caused in the input of the motor, in particular by acting on the control voltage, which is applied to control means 50 of feeder 51, when the arm 15 is swung in a given direction. Preferably, an auxiliary circuit 60 is closed by the switching means, whereby at least one of the resistances (in the example, the resistances 57 and 58 and the photoresistor 44) are bypassed, each time the arm 15 is swung in the direction Y, thus increasing e.g. in an amount of 25 percent, the value of voltage that is applied to motor M, by a corresponding increased of the voltage to control means 50.
Thus, each time the arm motion reveals a positive difference between the speeds Vf and Vr, independently from the absolute values thereof, a voltage increment is applied to the motor, and is maintained until a reversal in the swinging motion of arm 15 occurs, i.e. when the arm is swung in the X direction.
From a structural viewpoint, switching means I may advantageously comprise a short arm 61 (clearly shown in FIGS. 1 and 2), carried by the extension 41 of shaft 14 to which the arm 15 is fastened, and connected with the extension by a mounting means comprising e.g. a spring washer 62 that presses upon the hub 63 of arm 61, which is, in turn, pressed against a counter-ring 64 under the action of a spring 65, that, in turn, reacts against a ring 66 fixed to extension 41. Fast with the free end of arm 61, is a movable contact 67 that is connected with a conductor 60' of circuit 60, with the conductor 60" of circuit 60 being connected with a fixed contact 68. The amplitude of oscillation that can be performed by the arm 61 is limited, e.g. by an adjustable abutting means 69, and is restricted to a value smaller than that of cyclic oscillations x'-- y', which are caused by cyclic motion of yarn guide 11 of the distributor, as previously stated with reference to FIG. 1.
Thus, from what has been previously stated and from a perusal of accompanying drawings, it will be manifest that the input of motor M is made dependent on the dual control system, and more precisely on a basic system, with control means represented by the photoresistor 44, by which the middle operating position of arm 15 is established, according to the light-shielding degree of shutter 42, and on an intervention system, with control means comprising switching means I, and by which an increment of power is instantaneously and abruptly applied to Motor M every time the arm 15 is swung in the direction Y, this increment being also instantaneously and abruptly terminated every time the arm is swung in the opposite direction, and irrespective of the position of the arm at the start of such swinging motions.
According to another viewpoint, the second control system may be considered as an amplifier or booster of the intervention of the basic system, which means that the power which is fed to the motor is widely varied in conformity with the requirements, i.e. whether the bobbin is to be accelerated or decelerated to bring the arm back in its normal operating position, corresponding to the regular operation of the bobbin. Thus, a quick and powerful intervention is obtained, which is abruptly terminated when the arm-swinging motion is reversed.
According to a third viewpoint, the second control system, by taking advantage of cyclic oscillations x'-- x', will exert a stabilizing action on the arm by intervening, when the winder is in operation, in moments and through times which are automatically adapted to the changing frequency of motions A--B of the distributor and that, as well known, is proportional to the gradually reduced rotary speed of the bobbin which is being wound.
The above advantageous effects have been confirmed by repeated practical experimentation, which has evidenced the practically absolute stability of the operating winder, the quick return of the arm back in its middle position even after strong perturbations, and the practical absence of oscillations i.e. the practically instantaneous damping of return motions on attaining the middle operating position.
Moreover, the recourse to the motor input control system and to circuits of the type diagrammatically shown in FIG. 1 has proved to be highly advantageous since the intensity of current that flows through the circuit 60, controlled by the switch means I, can be limited to negligible values. Thus, no sparkings or other prejudicial actions occur between the contacts 67 and 68, and the device can operate with the highest degree of safety, without deteriorations or other troubles.