Patent Description:
As is known, the industrial type winding machines comprise a plurality of winding units where the yarn wound in a spool is unwound, subjected to a quality control, and subsequently rewound on a tube to form a reel. Typically, the yarn is collected by a thread guide cylinder, which drags the rotating reel by friction and governs the deposit of the thread so as to optimize the subsequent unravelling during the weaving step.

It is evident that at high collection speeds correspond to high unravelling speeds from the spool, and consequently high tension values in the yarn. In fact, the yarn, unwinding from the spool at pulsating height as a function of the length of the free section from the pick-up point, forms a so-called balloon. The increase in the diameter of the balloon causes a progressive increase in the tension of the yarn due to the centrifugal effect as the unravelling proceeds.

In addition, once a certain unravelling speed has been exceeded, the balloon collapses and slides against the spool tube, thus losing its characteristic shape: this causes a further increase in tension, which can lead to the deterioration and breakage of the yarn.

Typically, the winding units comprise the following constituent elements:.

In the absence of any tension control, drawing the yarn at the nominal collection speed vn and keeping the operating position of the thread tensioner constant at the nominal pressure pn, there is initially a lowering of the tension T below the average level of the spool due to the balloon-breaker, while in the final section the undesired increase in tension due to the progress of the unravelling is observed.

In order to homogenize the tension, and thus actuate a first form of control, it is customary on the one hand to compensate for the initial under-tensioning of the yarn due to the balloon-breaker by activating the thread tensioner at the maximum pressure (and not at the nominal pressure pn) and then progressively decrease it as the spool turns, on the other hand by decreasing the winding speed in the final section, when the thread tensioner has now reached the minimum set pressure and is no longer capable of absorbing further tension peaks.

In the absence of effective devices for controlling the unravelling tension, the decrease in speed represents an extremely limiting technological constraint with regard to the productivity of the winding unit and thus of the entire machine. Furthermore, such a forced reduction in speed is particularly disadvantageous because it can already amount to around <NUM>% of the spool's square footage.

These process restrictions are poorly combined with the increase in production capacity which the market currently requires of these machines so that they are increasingly economically attractive and performing.

It is well-known to adopt devices and processes, such as those illustrated in European patent application <CIT>, aimed at reducing the difference in tension between the start and end of the spool. In particular, the device in question comprises a square-section static balloon-breaker which overlies a pair of containment components which can be opened and closed in a radial direction with respect to the spool, in which these elements are configured to lower the tension of the yarn respectively in the initial and final unravelling steps. However, the document does not propose any methodology for using the device in order to achieve an increase in machine productivity.

The Chinese patent <CIT> discloses a method for controlling the winding tension of a yarn in which the yarn tension is controlled in a closed loop manner by a tension sensor and a yarn tensioner. A single-element balloon-breaker is used to control the yarn unwinding. The yarn tensioner is set according to measured values of the yarn tension sensor and the position of the balloon-breaker.

The need is therefore felt to resolve the drawbacks and limitations mentioned with reference to the prior art.

Therefore, there is a need to provide a method for controlling the winding tension of a yarn which is advantageous in terms of production times and thus is particularly advantageous in economic terms.

Furthermore, the need is felt for a method which can be easily implemented in existing machines, through an adequate programming of a programmable control unit of the winding machine.

Such requirements are satisfied by a method for controlling the winding tension of a yarn in a winding unit in accordance with claim <NUM>.

Further features and advantages of the present invention will be more clearly comprehensible from the description given below of preferred and non-limiting embodiments thereof, in which:.

The elements or parts of elements common to the embodiments described below will be indicated using the same reference numerals.

The method for controlling the winding tension of a yarn <NUM> according to the present invention will be described with reference to <FIG>, in which a winding unit <NUM> is shown comprising: a tension sensor <NUM>, a thread tensioner <NUM>, and an unravelling tension control device <NUM> comprising a first containment element <NUM> operable on command, and a second containment element <NUM> fixed and arranged downstream of the first containment element <NUM> along the winding direction of the yarn <NUM>.

In this discussion, the term thread or single thread or continuous thread refers to a single filament or continuous filament (for example in the case of silk, artificial or synthetic fibres), while the term yarn refers to a group of fibrils of varying lengths which are paralleled and joined together by twisting. Hereinafter, one or the other term will be used indifferently, it being understood that the applications of the present invention are not limited to one or the other type.

In this discussion, vmax refers to the maximum winding speed which can be set based on a certain type of yarn and process conditions. In other words, it is a maximum winding speed which can be predetermined based on information regarding the yarn and/or the spool and/or specific process conditions.

In accordance with a possible embodiment, in step (a) the pressure exerted by the thread tensioner (<NUM>) can be between pmin and pmax.

In step (b), upon reaching a predetermined tension value measured by the tension sensor <NUM>, the winding speed can be brought to a percentage of vmax between <NUM>% and <NUM>%.

Advantageously, in step (b), upon reaching a predetermined tension value measured by the tension sensor <NUM>, the winding speed can be brought to a predetermined percentage of vmax around <NUM>%.

In accordance with a possible embodiment of the method of the present invention, if in step (c) the tension is greater than a predetermined value and the pressure is equal to pmin, then the winding speed is further lowered.

The predetermined operating parameter of the winding, the obtaining of the first containment element <NUM> is operated can be the square footage of the spool.

In accordance with a possible embodiment, the operation of the first containment element <NUM> of the unravelling tension control device <NUM> can occur at a square footage of the spool between <NUM>% and <NUM>%, preferably around <NUM>%.

In accordance with a possible alternative embodiment, the predetermined operating parameter of the winding upon which the first containment element <NUM> is operated can be for example a winding time.

The first containment element <NUM> can substantially be tubular, having a longitudinal axis x and a first through opening <NUM> suitable for the passage of the yarn <NUM> exiting from a spool <NUM>.

The first containment element <NUM> can comprise a first containment component <NUM> and a second containment component <NUM>; in which the containment components <NUM>, <NUM>, can be movable between: a first position in which they are spaced apart from each other, and a second position in which they are close to each other with respect to the first position.

In other words, according to an aspect of the present invention, the operation of the first containment element <NUM> provides for the first containment element <NUM> and the second containment element <NUM> to move from the first position to the second position.

In accordance with a possible embodiment, in the second position the containment components <NUM>, <NUM> can be in contact with each other.

The containment components <NUM>, <NUM> can have an enlargement, and thus an increase in the diameter of the through opening <NUM> at the yarn inlet portion <NUM>.

In accordance with a possible embodiment, the containment components <NUM>, <NUM> can be arranged on respective first arm <NUM> and second arm <NUM>, which rotate with opposite directions, about respective rotation axes y, z spaced from each other, and substantially parallel to said axis x.

The first arm <NUM> and said second arm <NUM> can be provided with a cogwheel <NUM>, <NUM> integral with the respective arms, which mesh with each other and are adapted to rotate around the respective axes y, z, so that the rotation of the first arm <NUM> and of the second arm <NUM> is synchronous.

In accordance with a possible embodiment, the first containment element <NUM> can comprise movement means <NUM> arranged with a linear actuator <NUM> connected to one of the arms <NUM>, <NUM>. In particular, the linear actuator <NUM> can be connected to a lever <NUM>, arranged on one of the arms <NUM>, <NUM>, such that a linear movement of an operating end of the linear actuator <NUM> causes a rotation of the arm <NUM>, <NUM>. Advantageously, the linear actuator <NUM> can be of the electrical type.

Advantageously, the second static type containment element <NUM> is arranged with a second through opening <NUM> comprising a base portion <NUM> facing the first containment element <NUM> in use, and can have a substantially rectangular transverse section with respect to the longitudinal axis x.

Preferably, the second through opening <NUM> can have a substantially square transverse section with respect to the longitudinal axis x. In particular, the side of the substantially square transverse section of the second through opening <NUM> can have a dimension between <NUM> and <NUM>, preferably between <NUM> and <NUM>, and even more preferably around <NUM>.

The base portion <NUM> of the second through opening <NUM> can have a height, according to a longitudinal direction perpendicular to the transverse section of the through opening <NUM>, between <NUM> and <NUM>, preferably between <NUM> and <NUM>.

The second through opening <NUM> can comprise a substantially truncated-pyramid central portion <NUM> having a greater base at the base portion <NUM>, in an opposite position with respect to the yarn inlet section in the second containment element <NUM>. The central truncated-pyramid portion <NUM> can comprise a minor base having a substantially circular shape, opposite the major base.

The second through opening <NUM> can comprise a substantially cylindrical end portion <NUM>.

In accordance with a possible embodiment, the winding unit <NUM> can comprise a programmable control unit <NUM> operatively connected to the tension sensor <NUM>, the thread tensioner <NUM>, the tension control device <NUM>, and adapted to compare a value of an operating parameter measured with a reference value, and based on such a comparison, operating the first containment element <NUM> accordingly so that the first containment component <NUM> and the second containment component <NUM> pass from the first position to the second position, or to an intermediate position if present.

Thus, the advantages that can be achieved with the method of the present invention are now apparent.

Initially, by drawing the yarn at a collection speed greater than the nominal value, it is possible to exploit the initial undertension induced by the tension control device <NUM> to obtain a first benefit in terms of production capacity.

In this regard, in <FIG>, three graphs are schematically depicted showing possible trends in the winding speed, tension and pressure applied.

As can be seen, the initial speed is greater than the nominal speed which would normally be used in the initial winding step.

Subsequently, when the tension begins to increase, it is sufficient first to decrease the winding speed at the nominal speed (speed which would still be used) to actuate a first tension control, without changing the position of the thread tensioner.

Finally, in addition to a certain percentage of the square footage of the spool, the traditional adjustment of the tension by means of the thread tensioner <NUM> is assisted by the tension control device <NUM>, which absorbs those tension peaks which would otherwise cause the pressure of the thread tensioner <NUM> to decrease too quickly to the minimum value.

It is thereby possible to effectively distribute the pressure regulation interval over a wider time interval, delaying the achievement of the minimum pressure and thus the forced decrease of speed, remaining at the nominal speed practically until the end of the spool, further benefiting productivity.

Furthermore, it is possible to manage the tension control until the spool is exhausted in a simple and effective manner with the sole use of the thread tensioner, also reducing the operating field thereof in terms of stroke and encumbrance.

Furthermore, the method can also be implemented on existing machines by means of appropriate process parameter management.

The graph shown in <FIG> illustrates the advantages associated with the increase in productivity (expressed in terms of winding speed) which can be achieved with the use of the method of the present invention with respect to the prior art. In particular, it is seen that in the initial step and in the final step the winding speed (depicted with a continuous line) which can be used is substantially higher than the winding speed according to the prior art (depicted with a dotted line).

Claim 1:
Method for controlling the winding tension of a yarn (<NUM>) in a winding unit (<NUM>) comprising: a tension sensor (<NUM>), a thread tensioner (<NUM>), and an unravelling tension control device (<NUM>) comprising a first containment element (<NUM>) operable on command, and a second containment element (<NUM>) fixed and arranged downstream of the first containment element (<NUM>) along the winding direction of the yarn (<NUM>);
said method comprises the following steps:
(a) start of the winding step with winding speed equal to vmax;
(b) upon reaching a predetermined tension value measured by the tension sensor (<NUM>), the winding speed is brought to a predetermined percentage of vmax;
(c) upon reaching said predetermined percentage of vmax, from here on the unravelling tension is controlled by the thread tensioner (<NUM>); and
(d) upon reaching a predetermined operating parameter of the winding, operating the first containment element (<NUM>) of the unravelling tension control device (<NUM>).