BAREA, Tiziano (Via Valle Olona 17, Busto Arsizio, I-21052, IT)
1. A device (10) for feeding yarn (15) for textile applications, and for separating (d) the relative turns, comprising a wheel/drum (12) directly or indirectly motorized for rotation about its axis (16), the wheel/drum (12) presenting in its lateral surface a series of slits (20) to receive relative blades (22) the projecting profile of which enables the yarn turns (15) wound on the wheel/drum (12) to advance, the blades (22) forming an assembly which rotates together with the wheel/drum (12) but about an axis (26) having an inclination (a) and/or an eccentricity (e) relative to the axis (16) of the wheel/drum (12), such that the profile projection of the blades (22) from the relative slits (20) varies gradually along the perimeter of the wheel/drum (12), from a minimum to a maximum, to then gradually return to a minimum, but remains constant with time, characterised in that the blades (22) have a length ables to receive all the yarn turns (15) which concern the device (10). 2. A device (10) as claimed in claim 1 , wherein the wheel/drum (12) is coaxially fixed to the drive shaft (14), the blade (22) assembly being entrained by the wheel/drum (12).
3. A device (10) as claimed in claim 1 , wherein the blade (22) assembly is coaxially fixed to the drive shaft, the wheel/drum (12) being rotatably entrained by the blade (22) assembly.
4. A device (10) as claimed in claim 2, wherein the blade (22) assembly is coaxially fixed to an annular element (24) the axis (26) of which intersects the axis (16) of the wheel/drum (12) to form an angle (a) to the axis (16) of the drive shaft (14) to which the wheel/drum (12) is fixed, the annular element (24) being fixed coaxially to a bearing (28) rotatably carried by the drive shaft (14) such that it is able to rotate about said shaft (14) but with the required inclination (a).
5. A device (10) as claimed in claim 4, wherein the bearing (28) is of a material of low friction coefficient.
6. A device (10) as claimed in claim 2, wherein the entrainment takes place by interference between the blades (22) and the relative edge of the slits (20) involved in the entrainment, an element of a material with vibration damping properties being interposed between each blade (22) and the edge of the relative slit (20).
7. A device (10) as claimed in claim 2, wherein the entrainment of the blade (22) assembly by the wheel/drum (12) takes place by magnetic coupling.
8. A device (10) as claimed in claim 1 , wherein the lateral surface of the wheel/drum (12) presents projecting ribs (23) parallel to the axis (14), the yarn (15) wound in the form of turns resting only on said ribs (23), in addition to resting on the blades (22).
9. A device (10) as claimed in claim 1 , wherein means are provided for adjusting the inclination (a) of the axis (26) of the blade (22) assembly to the axis (16) and/or for adjusting the eccentricity (e) of the axis (26) to the axis (16), to consequently adjust the extent of separation (d) between the yarn turns (15) wound on the wheel/drum (12).
10. A device (10) as claimed in claim 1 , wherein in the case of a wheel/drum (12) of diameter between 30 mm and 60 mm, the eccentricity (e) is between 0 mm and 10 mm and the inclination (a) is between 0° and 30°, they cannot be null simultaneously.
The present invention relates to yarn feeders for textile applications and in particular to a device which enables both the yarn to be fed and its turns to be separated.
Various types of yarn feeder are known in the art for textile applications. All known feeders present a wheel, or cylinder, about which the yarn is wound in the form of one or more turns. It is therefore of fundamental importance to prevent these turns from being able to overlap each other and hence to "pinch" during feed. This can in fact cause yarn breakage or a defect in the finished product.
These wheel yarn feeders are therefore either provided with means to prevent the turns wound on the wheel from overlapping each other, or the wheel itself is made to perform this function.
Said wheel can be a rotating member (rotated by a motor), or a fixed member onto which an external member (also operated by a motor) loads the yarn, depending on the method of operation of the feeder.
Motorized wheel feeders with a fixed separator device are already known.
Specifically, this latter is a fixed bar disposed in the vicinity of the wheel and lying in the same plane as the axis of this latter, but inclined to this axis (in the most advanced versions this inclination is adjustable). The yarn, originating from a bobbin, is wound through one or more turns onto the wheel-bar assembly without straddling occurring, precisely because of the bar inclination.
Motorized wheel feeders are also known in which overlapping of the yarn turns is prevented by slightly inclining the wheel rotation axis to the horizontal. In this manner the point at which the yarn enters the wheel and the point a which it leaves it are in two different parallel vertical planes, so that the turns on the wheel do not overlap each other because they lie side by side, even if not separated.
In another known solution, a projecting ring, lying in a plane slightly inclined to a plane perpendicular to the wheel axis, is fixed to the peripheral surface of a motorized wheel/drum, so that on rotating the drum and consequently said ring, this latter causes the yarn forming the first turn (that closest to the yarn entry point) to be withdrawn by the inclined ring, while simultaneously urging the other turns already present on the drum to hence cause them to slide, side by side and mutually compacted, along the drum to the exit point. In a further known solution, a fixed drum has in its cylindrical surface a series of preferably angularly equidistant slits in which respective blades are disposed to rock in cyclic succession such as to project from the relative slit and consequently cause the yarn turns to advance towards the exit point. The cyclic blade rocking movement is independent of the unwinding of the yarn and is caused by an external motor member, generally the same used to operate the yarn turn loading member. This latter deposits the yarn onto the fixed drum, the rocking movement of the blades causing the turns to advance and be maintained separated from each other.
In their essential characteristics the aforedescribed solutions present various drawbacks, which are analyzed case by case below.
Although the solution comprising the motorized wheel with fixed bar separator has the advantage of achieving effective adjustable separation of the turns on the wheel, it has the drawback of generating friction due to the rubbing of the yarn on the fixed bar, which in fact limits the maximum number of turns which can be wound on the wheel, in addition to causing damage to the yarn, which is subjected to continuous mechanical stress. This friction also limits the minimum tension at which the device can operate and increases the energy consumption required to ensure wheel rotation. Finally, the greater the working tension and the number of turns, the greater is the power required at the motor.
In the case of the inclined motorized wheel solution, there is the drawback of not achieving proper separation (as stated, the turns are in mutual contact). Essentially, the small "transfer" surface between the wheel and yarn is utilized to enable the turns sliding on the wheel to advance, i.e. the yarn does not make contact with the wheel over its entire circumference, but touches it only at certain points because of projecting ribs (also called spokes in technical jargon) parallel to the wheel rotation axis. The result is that the first turn urges the subsequent turns, so compacting them. This type of feeder is also generally provided on purpose with a fixed bar separator to be used with certain yarn types. The motorized wheel with inclined ring solution also does not enable true separation to be achieved (as stated, again in this case the turns are in mutual contact) and hence has the same limits as the inclined motorized wheel solution, limits which become particularly significant with certain yarn types (for example elastic yarn), because of friction. A further drawback of this solution is that in unwinding from the bobbin via the feeder, the yarn undergoes twisting (this twist being added to or subtracted from the natural yarn twist) which can cause problems during production, representing in fact an alteration in the intrinsic characteristics of the yarn.
Although the solution comprising the fixed drum with cyclically rocking blades has the advantage of providing true mutual separation between the yarn turns, it also has the drawback of subjecting the yarn withdrawn from the bobbin to twisting (this twist being again added to or subtracted from the natural yarn twist). Another drawback is that this solution does not operate with certain yarn types (in particular elastic yarns) because as the drum is fixed, the rocking blades are unable to advance the yarn on the drum because of the friction between yarn and drum.
US-A-3971522 enables certain of the aforedescribed drawbacks to be overcome. Specifically, a solution is described (see the embodiment of Figure 3) comprising a motorized wheel/drum rotating about its axis and presenting a series of angularly equidistant slits to receive corresponding teeth of a wheel rotatable about an axis which is inclined to and eccentric to the axis of rotation of the wheel/drum. Consequently these teeth, or blades, project differently from the corresponding slits, this projection varying gradually in moving along the wheel/drum perimeter from a minimum to a maximum, to then return to a minimum, but which remains constant with time. These blades have a profile, in the direction of the relative wheel axis, which enables the lastly formed yarn turn to be separated from the previously formed turn, while at the same time advancing the turns, so that they pass from the blades to the wheel/drum, on which however they accumulate by coming into mutual contact (as shown by said Figure 6 of US-A-3971522), to give rise to the already described drawback.
US-A-2431712 also enables certain of the aforedescribed drawbacks to be overcome, by providing a rotatable wheel/drum with blades received in relative slits, but rocking such that the projection of the individual blade varies cyclically with time. Again in this case the yarn turns pass from the blades to the wheel/drum, to accumulate and come into mutual contact.
An object of the present invention is therefore to provide a yarn feeder- separator device which does not present the aforedescribed drawbacks. This object is attained by the yarn feeder-separator device in accordance with the accompanying claims.
The invention will be more apparent from the ensuing description of one exemplifying embodiment thereof. In this description reference is made to the accompanying drawings, in which:
Figure 1 is a side elevation of a device according to the present invention;
Figure 2 is a front view in the direction of the arrow 2 of Figure 1 ;
Figure 3 is a section therethrough on the line 3-3 of Figure 2;
Figure 4 is a view equal to that of Figure 1 , but with the yarn wound in separated turns.
As can be seen from the figures, the device 10 for feeding/distributing yarn for textile applications comprises a wheel/drum 12 fixed in conventional manner to a motorized shaft 14 the axis of which coincides with the axis 16 of the wheel/drum 12, so that this latter rotates rigidly with the shaft 14 when the relative motor is operated.
The lateral surface of the wheel/drum 12, about which the yarn 5 (Figure 4) is wound into turns, is of overall cylindrical shape with a flared edge 18 on the side on which the shaft 14 is located, and presents a series of angularly equidistant slits 20 (nine in number in the illustrated example). Each slit 20 receives a relative blade 22. The assembly of blades 22 rotates, by entrainment, together with the wheel/drum 12 when this latter is rotated. From the figures, it can also be seen that the radial projection of the individual blades 22 from the relative slit 20 gradually varies along the perimeter of the wheel/drum 12, to pass from a maximum projection of the upper blade 22 to zero projection of the lower blade 22, and to return to maximum projection of the upper blade. It is important to note that the projection of each blade 22 does not vary with time, so that it is not influenced by the rotation of the wheel/drum 12. This is because the blades 22 are fixed to an annular element 24 having an axis 26 inclined by an angle a to the axis 16 of the wheel/drum 12. The annular element 24 is itself fixed coaxially to a bearing 28 carried by the shaft 14 such that it is able to rotate freely about this shaft, but with the required inclination a. It should be noted that the relative rotation between the bearing 28 and shaft 14 is limited to the clearances existing between the blades 22 and the relative slits 20 (i.e. extremely limited), such that just a suitable bronze bush or a suitable ring of low friction coefficient material (e.g. teflon) can be used, however a suitably shaped rolling bearing can be used if required.
From Figures 1 and 3 it can be seen that the blades 22 have an external profile slightly inclined to the axis 16 to facilitate advancement of the yarn turns on the wheel/drum 12.
It should be noted that instead of inclining the axis 26 of the blade 22 assembly to the axis 16, the same result can be achieved simply by not making the axis 26 of the blade 22 assembly intersect the axis 16 of the wheel/drum 12 (so that in this case there is a minimum distance, or eccentricity, between the two, to be indicated by "e"), or again by inclining said two axes and also providing said eccentricity between them. Although such an eccentricity e, even if present, could not in reality be seen on observing the figures, it has been indicated for representative purposes in Figure 3.
As is apparent to an expert in mechanics, means (not shown for simplicity) could be provided to adjust the angle a and/or the eccentricity e (for example a screw regulator means or a mechanical actuator), with the advantage of being able to adjust the extent of separation between the yarn turns.
It should also be noted that the drive shaft can be made coaxial to the axis of the blade 22 assembly, and the wheel/drum 12 be rotatably driven about an axis 16 eccentric to and/or inclined to the axis 26.
To reduce the friction between the yarn 15 and the external surface of the wheel/drum 12 as much as possible in order to facilitate yarn advancement during separation, this surface can be provided parallel to the axis 16 with projecting ribs 23 (spokes) on which just the yarn rests (evidently in addition to resting on the blades 22).
From tests carried out, it has been found that the number of blades and the ratio between the wheel/drum surface area in contact with the yarn and the blade surface area in contact with the yarn are a function of the minimum value of the separation distance d to be guaranteed between the turns.
The tests have also shown that the value of the two parameters, eccentricity e and inclination a, are fundamentally important for correct separation of the yarn turns. In particular, the eccentricity e is a function of the diameter of the wheel/drum 12 while the inclination a decides the distance (d) by which the turns must be separated from each other. For example, for a wheel/drum with a diameter between 30 and 60 mm it has been found that to ensure good separation the eccentricity e must be between 0 and 10 mm and the inclination a between 0° and 30°, it being understood that they cannot be null simultaneously.
It should also be noted that rotary motion transmission from the wheel/drum 12 to the blade 22 assembly (or vice versa) can be achieved not only by direct contact between blades and relative sides of the slits 20 (as in the embodiment illustrated in the figures, possibly by interposing elements of a material having vibration damping properties, such as silicone rubber or neoprene sponge elements) but also by magnetic coupling.
It is important to note that the feeder-separator device according to the present invention enables effective separation d to be obtained, and maintained, of all those yarn turns concerning the device 10 (this separation, as aforestated, even being adjustable), in addition to reducing the unwinding tension of the yarn 15 to a minimum and enabling even a large number of turns to be obtained on the device 0, provided the blades 22 are of sufficient length to receive all the turns wound onto the device 10 (in any event a number of turns greater than that obtainable with known devices), hence preventing slippage of the yarn 15.
It should further be noted that the number of turns does not affect the rotation force of the wheel/drum 12, precisely because the wheel/drum is not fixed but rotates together with the blades 22, and that the yarn 15 does not undergo any twisting (as it enters or exits),. The yarn turn separation action is synchronized with the wheel/drum rotation and hence with the yarn feed. Finally it is important to note that by virtue of the wheel/drum rotation, the device of the invention operates without problems using any yarn type (in particular elastic yarns), as it is not influenced by friction.
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