Accumulation yarn feeder provided with loop spacing device

Abstract

An accumulation yarn feeder (10), comprising: - a drum (12) having an input end (12a), an output end (12b) opposite to the input end (12a), and a lateral winding surface provided with a plurality of longitudinal slots (28), - winding means (14) adapted to wind a yarn (Y) onto the lateral winding surface of the drum (12) in the form of loops (YL), - a loop spacing device (18) provided with a plurality of longitudinal yarn supporting arms (26) supported around an oscillation axis (X), each of which is received in a respective one of the longitudinal slots (28), and with an oscillation mechanism (30) which actuates the longitudinal yarn supporting arms (26) with an oscillating motion which causes the progressive advancement of the yarn loops (YL) from the input end (12a) to the output end (12b) of the drum (12); each of the longitudinal yarn supporting arms (26) has a longitudinal input portion (26a) directed toward the input end (12a) of the drum (12), which has an outer surface that is curved around the oscillation axis (X), and a longitudinal output portion (26b), which is directed toward the output end (12b) of the drum (12) and has a concave outer surface delimited between two longitudinal ribs (26b', 26b").

Description

[0001] The invention relates to an accumulation yarn feeder provided with a loop spacing device.

[0002] As is known, in a generic weaving process, a yarn can be fed to a textile machine by a yarn feeder of the so-called "accumulation" type.

[0003] In a generic accumulation yarn feeder, multiple yarn loops are wound onto a drum to form a reserve. The yarn, when requested by the textile machine, unwinds from an output end of the drum, passing through a weft braking device which controls its tension.

[0004] As the drum empties, winding means take new yarn from a spool and wind it at an input end of the drum which is opposite the output end. Depending on the type of feeder, the winding means may comprise a motorized weft winding flywheel or a system adapted to turn the drum itself.

[0005] In order to ensure smooth and regular unwinding of the yarn from the drum, also in relation to the tension control to which the yarn is subjected, the yarn loops on the drum are kept axially spaced apart by a loop spacing device.

[0006] In a per se known manner, e.g. from EP 0829442 B1, the loop spacing device may comprise a series of longitudinal yarn supporting arms which are supported around an oscillation axis and are received in respective longitudinal slots of the drum. When actuated by an oscillation mechanism, the longitudinal yarn supporting arms perform an oscillating movement while the yarn is wound onto the drum and said movement causes the loops to advance progressively from the input end to the output end of the drum.

[0007] Each of the longitudinal yarn supporting arms may generally comprise a metal plate provided with a wear-resistant coating (e.g., chrome plating, DLC (Diamond-Like Carbon), or the like) on its outer surface.

[0008] In some known solutions, the outer surface of the plate is slightly arclike around the oscillation axis (i.e., with the convexity directed outward).

[0009] This solution has the advantage that the tension of the yarn wound on the drum is discharged over the entire width of the metal plate, so as to reduce the risk of wear or damage to the metal plate and the wear-resistant coating. On the other hand, in the presence of dusty yarns, a large amount of fine dust is generated due to friction between the yarn and the metal plate along the contact surface, which is relatively large.

[0010] In other known solutions, the outer surface of the metal plate is concave and delimited between two longitudinal ribs. In this case, therefore, the yarn engages only the ridge surfaces of the two ribs.

[0011] By reducing the contact surface between the yarn and the metal plate, this solution has the advantage of generating much less fine dust even in the presence of dusty yarns. On the other hand, in this case, the wear-resistant coating of the metal plate can easily be damaged and, in the presence of particularly aggressive yarns such as jute, steel wire or the like, the metal plate can even be cut.

[0012] In view of the above, the aim of the present invention is to provide an accumulation yarn feeder provided with a loop spacing device capable of minimizing the above-mentioned drawbacks of known solutions and, at the same time, combining their advantages.

[0013] This aim and other objects, which will become better apparent hereinafter are achieved by an accumulation yarn feeder having the characteristics presented in claim 1, while the dependent claims define other advantageous characteristics of the invention.

[0014] The invention will now be described in greater detail with reference to a preferred but not exclusive embodiment thereof, illustrated by way of nonlimiting example in the accompanying drawings, wherein: Figure 1 is a perspective view of an accumulation yarn feeder provided with a loop spacing device according to the invention; Figure 2 is a lateral elevation view of the yarn feeder of Figure 1; Figure 3 is a sectional view of Figure 1, taken along the plane III-III; Figure 4 is a sectional view of Figure 1, taken along the plane IV-IV; Figure 5 is a perspective view of an isolated detail of the loop spacing device according to the invention; Figure 6 is an enlarged-scale view of a detail of Figure 4.

[0015] With initial reference to Figure 1, a yarn feeder 10 of the accumulation type comprises a drum 12 provided with an input end 12a, an output end 12b which is opposite the input end 12a, and a lateral winding surface provided with a plurality of longitudinal slots 28.

[0016] Winding means take yarn Y from an upstream spool (not shown) and wind it onto the lateral winding surface of the drum 12 in the form of loops YL to form a reserve (the yarn Y and the loops YL are shown only in Figure 2). In a per se known manner, the winding means may comprise a weft winding flywheel 14 located adjacent to the input end 12a of the drum 12 and driven in rotation by a drive shaft 22.

[0017] At the request of a generic downstream textile machine (not shown), the yarn Y unwinds from the output end 12b of the drum 12 and passes through a weft braking device 16 which controls its tension.

[0018] In order to ensure smooth and regular unwinding of the yarn Y from the drum 12, also in relation to the tension control to which the yarn Y is subjected, the loops of yarn YL on the drum 12 are kept axially spaced apart by a loop spacing device 18.

[0019] In a per se known manner, the loop spacing device may comprise a series of longitudinal yarn supporting arms 26 which are supported around an oscillation axis X and are each received in a respective longitudinal slot 28.

[0020] In greater detail, the longitudinal yarn supporting arms 26 are supported by a hub 20 by means of respective spokes 24.

[0021] Again in a per se known manner, during the rotation of the weft winding flywheel 16, an oscillation mechanism 30 (only partially visible in the Figures) actuates the longitudinal yarn supporting arms 26 with an oscillating motion that causes the progressive advancement of the loops YL from the input end 12a to the output end 12b of the drum l2.

[0022] The oscillation mechanism 30 may be of the type per se known from EP 0829442 B1 and may comprise a rolling bearing which is inserted in the hub 20 and engages, with its inner ring, a bushing which is fitted on the drive shaft 22 and has an outer cylindrical surface which has an axis that is oblique with respect to the axis of the drive shaft 22. By virtue of the engagement between the bushing and the rolling bearing, the longitudinal thread supporting arms perform the said oscillating movement.

[0023] According to the invention, with particular reference to Figure 5, each of the longitudinal yarn supporting arms 26 has a longitudinal input portion 26a directed toward the input end 12a of the drum 12, which has an outer surface that is curved around the oscillation axis X, and a longitudinal output portion 26b directed toward the output end 12b of the drum 12, which has a concave outer surface delimited between two longitudinal ribs 26b', 26b".

[0024] Preferably, in this embodiment the outer surface of the longitudinal input portion 26a has a cylindrical profile that is substantially coaxial to the oscillation axis X. More preferably, the cylindrical profile of the outer surface of the longitudinal input portion 26a has a diameter that is substantially equal to the lateral winding surface of the drum 12.

[0025] Preferably, each of the longitudinal ribs 26b', 26b" has a ridge surface 36', 36" which is substantially flat or slightly curved around the oscillation axis X.

[0026] Advantageously, the longitudinal input portion 26a and the longitudinal output portion 26b are interconnected by a short blending portion 26c in which the ridge surfaces 36', 36" of the two ribs 26b' and 26b" progressively widen inward until they blend with the outer surface of the input portion 26a.

[0027] In this embodiment, each of the longitudinal yarn supporting arms 26 is composed of a metal plate which is screwed onto the respective spoke 24 of the hub 20 and bent so as to have an outer surface shaped as defined above. Advantageously, the outer surface of the metal plate may be provided, in a per se conventional manner, with a wear-resistant coating such as chrome plating, DLC (Diamond-Like Carbon), and the like.

[0028] The operation of the loop spacing device is similar to that of known devices, but it minimizes their disadvantages and combines their advantages, according to the intended aim and objects.

[0029] In particular, when the yarn loops YL engage the longitudinal input portions 26a of the longitudinal yarn supporting arms 26, the tension of the yarn Y is discharged over the entire width of the plate, thereby reducing the risk of wear or damage to the metal plate 36 and the wear-resistant coating.

[0030] When the loops of yarn YL disengage the longitudinal input portions 26a and engage the longitudinal output portions 26b of the longitudinal yarn supporting arms 26, the tension of the yarn Y decreases because, from a geometric point of view, the chord subtended between the longitudinal ribs 26b', 26b" is shorter than the arc on which the yarn Y rests in the longitudinal input portions 26a. In other words, by passing from the longitudinal input portions 26a to the longitudinal output portions 26b, the yarn loops YL assume a looser configuration, with a consequent decrease in the tension of the yarn Y.

[0031] Consequently, although the tension of the yarn Y is discharged only over the width of the ridge surfaces 36', 36" of the two ribs 26b', 26b", the wear of the coating is very limited and the risk of damage to the metal plate 36 is substantially nil. At the same time, the fine dust generated by the yarn Y when it engages the longitudinal output portions 26b is extremely low.

[0032] A preferred embodiment of the invention has been described, but of course the person skilled in the art may make various modifications or variations within the scope of the claims.

[0033] For example, as will be readily understood by the person skilled in the art, the motorized yarn winding flywheel could be replaced by different winding means, such as a system adapted to turn the drum.

[0034] Moreover, in the description and in the claims, the outer surface of the longitudinal yarn supporting arms, at the longitudinal input portion, is defined as curved around the axis of oscillation. This definition should not be understood as limited to a cylindrical profile that is coaxial with the axis of oscillation. On the contrary, it should be extended generally to any curved profile having its convexity directed outward, by virtue of which the yarn and the longitudinal yarn supporting arm are in contact substantially over the entire width of the longitudinal yarn supporting arm. For example, at the longitudinal input portion, the outer surface of the longitudinal yarn supporting arm could have a cylindrical profile with a radius slightly greater or slightly smaller than that of the drum, or an elliptical or parabolic sectional profile.

[0035] Moreover, the longitudinal yarn supporting arms might be made of a material other than metal plate, for example ceramic material.

[0036] The disclosures in Italian Patent Application No. 102024000022647 from which this application claims priority are incorporated herein by reference.

[0037] Where technical features mentioned in any claim are followed by reference signs, such reference signs have been inserted for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. An accumulation yarn feeder (10), comprising: - a drum (12) having an input end (12a), an output end (12b) opposite to the input end (12a), and a lateral winding surface provided with a plurality of longitudinal slots (28), - winding means (14) adapted to wind a yarn (Y) onto said lateral winding surface of the drum (12) in the form of loops (YL), - a loop spacing device (18) provided with a plurality of longitudinal yarn supporting arms (26) supported around an oscillation axis (X), each of which is received in a respective one of said longitudinal slots (28), and with an oscillation mechanism (30) which actuates said longitudinal yarn supporting arms (26) with an oscillating motion which causes the progressive advancement of said yarn loops (YL) from said input end (12a) to said output end (12b) of the drum (12), characterized in that each of said longitudinal yarn supporting arms (26) has a longitudinal input portion (26a) directed toward said input end (12a) of the drum (12), which has an outer surface that is curved around said oscillation axis (X), and a longitudinal output portion (26b), which is directed toward said output end (12b) of the drum (12) and has a concave outer surface delimited between two longitudinal ribs (26b', 26b").

2. The accumulation yarn feeder (10) according to claim 1, characterized in that the outer surface of said longitudinal input portion (26a) has a cylindrical profile that is substantially coaxial to said oscillation axis (X).

3. The accumulation yarn feeder (10) according to claim 2, characterized in that said cylindrical profile of the outer surface of said longitudinal input portion (26a) has a diameter substantially equal to said lateral winding surface of the drum (12).

4. The accumulation yarn feeder (10) according to claim 1, characterized in that each of said longitudinal ribs (26b', 26b") has a ridge surface (36', 36") that is flat or slightly curved around said oscillation axis (X).

5. The accumulation yarn feeder (10) according to claim 4, characterized in that said longitudinal input portion (26a) and said longitudinal output portion (26b) are interconnected by a blending portion (26c) in which said ridge surfaces (36', 36") progressively widen inward until they blend with the outer surface of said input portion (26a).

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