EP2719804B1

EP2719804B1 - Weft-braking device for yarn feeders with stationary drum

Info

Publication number: EP2719804B1
Application number: EP13003739.3A
Authority: EP
Inventors: Rosario Castelli; Giovanni Pedrini
Original assignee: LGL Electronics SpA
Current assignee: LGL Electronics SpA
Priority date: 2012-10-09
Filing date: 2013-07-26
Publication date: 2015-12-30
Anticipated expiration: 2033-07-26
Also published as: CN103710821A; CN103710821B; EP2719804A1; ITTO20120875A1

Description

The present invention relates to a weft-braking device for yarn feeders provided with a stationary drum.
Yarn feeders are known, which comprise a stationary drum on which a motorized swivel arm winds a plurality of yarn loops forming a stock. Upon request from a general textile machine arranged downstream, the loops are unwound from the drum, then pass through a weft-braking device adapted to maintain the unwinding yarn slightly tensioned, and then are fed to the machine.
A general weft-braking device comprises a hollow, frustoconical braking member, usually called "cone", which is coaxially arranged in front of the drum and is elastically biased with its inner surface against the delivery edge of the drum.
In a known weft-braking device, such as the one disclosed in IT2004TO00105U or EP-A-0884263 of Applicant, the smaller base of the cone is coaxially attached to a ring which is supported at the middle of a spider assembly of helical springs pulling on an outer annular support. The annular support is attached to a slide which may shift upon control of a manual adjusting mechanism, in order to adjust the static pressure exerted by the frustoconical braking member against the drum. The yarn running between the drum and the braking member thereby receives a braking action by friction.
The known devices, such as the one disclosed in the above-cited patent, have drawbacks. In particular, fastening/unfastening the cone, e.g., for replacement or cleaning purposes, are inconvenient operations. In fact, it is required to unhook the ends of the springs, which are usually in the shape of narrow hooks, from respective holes formed in the inner ring and in the outer annular support, which holes are usually very small, in order to prevent accidental unhooking as well as to avoid gaps which could affect the accuracy and uniformity of the braking action along the circular shape of the cone. Such drawback is further made worse by the circumstance that, in order to improve the uniformity of the braking action, at least six springs are generally used, with further lengthening of the time for the fastening/unfastening operations and, consequently, longer machine downtimes.
Moreover, when used in association with some types of yarn, the dust generated by the yarn scraping against the cone and the drum is liable to get entangled with the pointed ends of the springs, and then to build up into a big mass which covers the whole braking device. Of course, this circumstance is undesirable because it makes it necessary to carry out frequent manteinance/cleaning operations, and has the further drawback that the accumulated dust can be partially detached and carried by the yarn into the fabric, thereby affecting the quality of the item.
Another weft-braking device of the type mentioned above is disclosed in EP 0 884 263 of Applicant, in which the frustoconical member is coupled to an adjustable annular support by means of at least two sets of identical traction springs having respective different stiffnesses and preloads which are inversely proportional to the respective stiffness of the springs.
Therefore, it is a main object of the invention to provide a weft-braking device which overcomes the above-cited drawbacks of the known devices, by making it easier to install/uninstall the cone, e.g., for replacement or cleaning purposes, and by preventing the accumulation of dust at the elastic elements.
The above object and other advantages which will better appear from the following description are achieved by the weft-braking device having the features recited in claim 1, while the dependent claims state other advantageous, though secondary features of the invention.
The invention will be now described in more detail, with reference to a few preferred, non-exclusive embodiments shown by way of non-limiting example in the attached drawings, wherein:

Fig. 1 is a diagrammatical view in side elevation of a yarn feeder with stationary drum, of the type referred to by the present invention, on which a general weft-braking device is installed;
Fig. 2 is a perspective view of a weft-braking device according to the invention;
Fig. 3 is a perspective view showing a component of the weft-braking device of Fig. 1;
Fig. 4 is an exploded, perspective view showing a detail of the component of Fig. 3 to an enlarged scale.

A general yarn feeder YF of the type referred to by the present invention is diagrammatically shown in Fig. 1. Yarn feeder YF is provided with a stationary yarn-winding drum D, on which a motorized swivel arm A winds a plurality of loops of yarn F forming a stock. Upon request from a general textile machine arranged downstream (not shown), e.g., a conventional knitting machine, the loops are unwound from drum D, then pass through a weft-braking device 10 which is adapted to maintain the unwinding yarn slightly tensioned, and then are fed to the machine.
A weft-braking device 10 according to the invention is shown in detail in Figs. 2-4. Weft-braking device 10 generally comprises a hollow, frustoconical braking member or cone 12, which is coaxially supported in front of weft-winding drum D, as diagrammatically shown in Fig. 1, and is elastically biased with its inner surface against the delivery edge of the drum. To this purpose, as shown in Fig. 2, the smaller base 12a of cone 12 is coaxially attached to a ring 14, which is supported at the middle of an annular support 16 via elastic means. Annular support 16 is adapted to be connected, in a way known per se, to an annular frame T (diagrammatically shown in Fig. 1) which, in turn, is connected to the housing of the feeder. To this purpose, annular support 16 has a flange 17 formed at its axial end facing the drum, which is provided with three toothed tabs 18 spaced at equal angles from each other and projecting longitudinally from its outer edge to engage corresponding seats (not shown) of annular frame T by snap fit. Annular frame T is typically attached to a mechanism M (diagrammatically shown in Fig. 1) which allows the axial position of annular support 16 with respect to drum D to be manually varied, in order to adjust the static pressure exerted by cone 12 against the edge of the drum.
According to the invention, the elastic means which connect inner ring 14 to outer annular support 16 comprise a triad of elongated elastic members, which preferably consist of helical springs 19, each of which has both its ends anchored to respective anchor seats 20 of annular support 16 which are arranged in pairs equally-spaced from each other, and has an intermediate portion that restrainedly engages a respective one of three anchor projections 22 formed on the ring 14 and spaced 120° from each other.
Preferably, all six anchor seats 20 on outer annular support 16 are equally spaced 60° from each other.
Advantageously, both inner ring 14 and outer annular support 16 are molded in a synthetic material, and anchor projections 22 are made enbloc with inner ring 14, as well as anchor seats 20 with outer annular support 16.
Anchor projections 22 are in the shape of hooks projecting outwards.
A through opening in the shape of a radial hole 24 is formed on annular support 16 at each anchor seat 20, through which a corresponding end of spring 19 is inserted. Two counterposed, longitudinal guides 26a, 26b having their upper ends bent at right angles inwards are formed at respective opposite sides of hole 24. Guides 26a, 26b extend longitudinally from flange 17 to the opposite axial end of annular support 16. The ends of springs 19 are conventionally provided with eyelets 28 (Fig. 3). Eyelets 28 are anchored to their respective seats 20 via anchor members in the shape of pins 30. The pins are inserted in eyelets 28, abut against the surface of annular support 16 facing away from the side of insertion of springs 19, and engage guides 26a, 26b with their opposite ends.
In operation, the yarn runs between the drum and the braking member and, therefore, is subject to a braking action by friction, in a conventional way per se.
However, with the weft-braking device according to the invention, connecting springs 19 to annular support 16 via pins 30 is only required at first installation, after which cone 12 can be fastened/unfastened more easily and more practically with respect to the conventional weft-braking devices (e.g., for replacement or cleaning purposes) by simply hooking/unhooking springs 19 to/from hook-shaped projections 22 of inner ring 14.
In addition, although the device according to the invention is only provided with three elastic members, it should be noted that they pull on the annular support in six points, for the benefit of a uniform distribution of the forces.
Moreover, as the person skilled in the art will appreciate, with the device according to the invention annular support 16 acts as a shield for the pointed ends of the springs, against the dust generated by the yarn running between the drum and the cone, thereby preventing heaps of dust from building up on the brake, with consequent drawbacks.
A preferred embodiment of the invention has been described herein, but of course many changes may been made by a person skilled in the art within the scope of the claims. In particular, the number of elastic members may be reduced to two or increased, e.g., to four or even more, depending on the circumstances. Although helical springs are used in the above-described example, other types of elongated, elastic members can be used, such as elastic ropes made of rubber, which could be provided with rigid, anchor ends in the shape of hooks or rings. Moreover, in the above-described example the opposite ends of each spring are anchored to two respective seats spaced from each other. However, both ends could be anchored to the same seat. Furthermore, cone 12 could also be made enbloc with inner ring 14. Moreover, in the present description reference has always been made to a hollow, frustoconical braking member. However, it is obvious that the same system can be applied to circular braking members having different shapes, e.g., members in the shape of bell or dome, which may be made of either a continuous material, e.g., plastics, or a non-continuous material, e.g., bristles. In addition, the anchor ends of springs 19 are not necessarily required to be in the shape of eyelets, provided that they are bent to a restrainedly engageable shape, e.g., a hook shape. Furthermore, through openings 24 could also consist of recesses on one of the edges of annular support.

Claims

A weft-braking device for yarn feeders having a stationary drum, comprising a braking member having a circular profile (12), which is coaxially supported via elastic means at the middle of an annular support (16) connectable to said yarn feeder, and is adapted to be coaxially biased against the delivery edge of said stationary drum of the feeder for applying a braking action by friction to the yarn, characterized in that said elastic means comprise at least two elongated elastic members (19), which have both their ends anchored to said annular support (16), and have intermediate portions restrainedly engaged with respective anchor projections (22) integral with said braking member (12).
The weft-braking device of claim 1, characterized in that said annular support is provided with anchoring seats (20) in which the ends of said elongated elastic members are restrained.
The weft-braking device of claim 2, characterized in that, at each of said anchor seats (20), said annular support (16) has a through opening (24) in which one end of said elongated elastic member (19) is inserted, said end being anchored to an anchoring member (30) adapted to abut against the opposite surface of said annular support (16) with respect to the insertion side.
The weft-braking device of claim 3, characterized in that said elongated elastic members (19) are provided with curved anchoring ends (28), and said anchoring member consists of a pin (30) engaging the respective curved anchoring end (28) and abutting with its opposite ends against said opposite surface of the annular support (16).
The weft-braking device of claim 4, characterized in that said anchoring seats (20) each comprise two counterposed guides (26a, 26b) which longitudinally extend on said opposite surface of the annular support (16) at the opposite sides of the through opening (24), and are engaged by the opposed ends of said pin (30).
The weft-braking device of any of claims 1 to 5, characterized in that said anchoring projections (22) are hook-shaped and are formed in one piece on a molded ring (14) made of a synthetic material, which is coaxially connected to the braking member (12).
The weft-braking device of any of claims 2 to 6, characterized in that said anchoring projections (20) are arranged in pairs equally-spaced from each other.
The weft-braking device of claim 7, characterized in that all of said anchoring seats (20) are equally-spaced from each other.
The weft-braking device of any of claims 1 to 8, characterized in that it comprises three of said elongated elastic members (19).
The weft-braking device of any of claims 1 to 9, characterized in that said elongated elastic members are helical springs (19).