EP1724384A1

EP1724384A1 - Yarn-braking device in weft feeders for textile machines

Info

Publication number: EP1724384A1
Application number: EP06005694A
Authority: EP
Inventors: Giovanni Pedrini; Pietro Zenoni
Original assignee: LGL Electronics SpA
Current assignee: LGL Electronics SpA
Priority date: 2005-05-18
Filing date: 2006-03-21
Publication date: 2006-11-22
Anticipated expiration: 2026-03-21
Also published as: CN1865110B; DE602006001031T2; CN1865110A; DE602006001031D1; EP1724384B1; ITTO20050063U1

Abstract

A weft feeder is provided with a weft-storing drum (12) having a delivery edge (12a) from which the yarn (F) is unwound to be fed to a textile machine. A yarn-braking device comprises a frustoconical, hollow braking member (32) supported with its larger base facing the drum and coaxially biased with its inner surface against the delivery edge (12a) of the drum. The edge (26a) of the larger base of the braking member (26) is lined with a protection ring (32) having an inner, circumferential slot (34) formed in the direction of the generatrices of the cone in which the edge of the larger base (26a) is received.

Description

The present invention relates to a yarn-braking device in weft feeders for textile machines.
As known, yarn feeders for textile machines comprise a stationary drum on which a motorized swivel arm winds a plurality of yarn loops forming a weft reserve. Upon request from the loom, the loops are unwound from the drum, then pass through a braking assembly which controls the tension of the yarn in order to maintain it substantially constant, and finally are fed to the loom.
In the weft feeders of the above type, which are known from prior patents of Applicant such as IT1251209 and IT1259567 , the braking member typically comprises a frustoconical hollow member which is coaxially supported with its larger base facing the drum, and is biased with its inner surface against the end of the drum, from which the loops are unwound. The unwinding yarn runs between the drum and the frustoconical member, which apply the desired braking action upon the yarn.
In order to improve the uniformity of the braking action, also in relation to yarn having different thicknesses, the frustoconical member is made of a limitedly deformable material, such as a tissue or a laminated plastic impregnated with a polymeric resin, so that it can be warped by the running yarn, whereby the pressure upon the drum is maintained substantially constant.
The yarn, which rotates while unwinding from the drum, is projected outwards by the centrifugal force in the shape of a body of revolution -usually called "balloon"- which, as known, may cause the formation of tangles, knots, and the like. In order to overcome this drawback, it is known from further prior patents of Applicant, such as IT1311244 and IT1319948 , to provide the drum with an anti-balloon ring surrounding the drum immediately upstream of the frustoconical member, in order to contain the yarn in contrast with the centrifugal force.
However, the unwinding yarn, which is subject to the centrifugal force, is liable to enter the annular gap between the anti-balloon ring and the larger base of the frustoconical member. This circumstance causes the yarn, which is projected outwards, to glide against the edge of the larger base of the braking member, thereby causing the latter to progressively wear and the correct operation of the braking member to be consequently affected.
The edge of the larger base of the frustoconical member is also at risk of damages during the manual installation of the braking member. In fact, such operation is carried out manually by means of a tool having a hook-shaped end portion which may get entangled with the edge of the frustoconical member, thereby scratching the frustoconical member.
Therefore, it is a main object of the present invention to improve the above yarn-braking device by protecting the main edge of the frustoconical braking member from damages without affecting the deformability of the frustoconical member, which is required to provide uniform braking actions.
The above object and other advantages, which will better appear below, are achieved by the improved yarn-braking device having the features recited in claim 1, while the other claims state other advantageous features of the invention.
The invention will be now described in more detail, with reference to a preferred, non exclusive embodiment shown by way of non limiting example in the attached drawings, wherein:

Fig. 1 is a side elevation view of a yarn feeder provided with an improved yarn-braking device according to the invention;
Fig. 2 shows a detail of Fig. 1 to an enlarged scale.

With reference to the above Figures, a yarn feeder 10 for textile machines comprises a stationary, weft-storing drum 12 on which a swivel arm 14 driven by a motor 15 winds a plurality of yarn loops forming a weft reserve RT. The delivery edge of drum 12 is beveled in 12a. Upon request from the loom (not shown), yarn F is unwound from drum 12 and passes through a yarn-guide eyelet 16, which is supported coaxially with drum 12 by a stationary arm 17 projecting from the motor housing in a direction parallel to the axis of the drum.
Stationary arm 17 also supports a braking assembly 18 having the task of controlling the tension of the yarn while unwinding from drum 12, in order to maintain it substantially constant.
In a known way, braking assembly 18 comprises an annular support 20 supported coaxially with drum 12 by a slide 22 that is slidable along stationary arm 17 under control of a worm-screw mechanism (not shown) operable by a knob 24. A frustoconical hollow member 26 is supported at the center of annular support 20 by a spider-assembly of springs 28 (only diagrammatically shown in the Figures) each having one end anchored to support 20 and the opposite end anchored to the smaller base of frustoconical member 26. The frustoconical member is arranged with its larger base facing the drum and is elastically biased with its inner surface against beveled edge 12a.
Frustoconical member 26 is preferably made of a tissue or laminated plastic impregnated with a polymeric resin, and its contact area with the drum is lined with an inner, wearproof lining consisting of a metal foil 29 (Fig. 2) applied on the edge 26a of the larger base of the frustoconical member.
Stationary drum 17 also supports an anti-balloon ring 30 surrounding drum 12 upstream of frustoconical member 26. An annular gap L is defined between anti-balloon ring 30 and the larger base of the frustoconical member.
In a known way, yarn F runs between beveled edge 12a of drum 12 and frustoconical member 26, which apply the desired braking action upon it. By operating knob 24, the static contact pressure applied upon the drum by the frustoconical member may be adjusted.
According to this invention, edge 26a of the larger base of frustoconical member 26 is lined with a protection ring 32 having an inner, circumferential slot 34 projecting in the direction of the generatrices of the cone, in which edge 26a is received.
As shown in detail in Fig. 2, the height H of slot 34 is slightly greater then the thickness S of frustoconical member 26 in the area lined with the wearproof foil 29. Therefore, the frustoconical member is not stiffened by ring 32 and, consequently, the frustoconical member can be freely warped by the running yarn F, as required for maintaining the pressure upon the drum substantially uniform and constant.
Protection ring 32 is molded from an elastomeric material, preferably polyurethan, so that it can be elastically expanded to be manually mounted on edge 26a, thereby making it easier to install the ring and to replace it.
slot 34 is defined between two parallel, circumferential lips 32a, 32b which engage the opposite surfaces of edge 26a. Preferably, outer lip 32a protrudes beyond inner lip 32b, for easier handling of the ring during installation.
In the operation, when yarn F is projected outwards by the centrifugal force into the annuler gap L defined between the anti-balloon ring and the larger base of the frustoconical member, as shown in Fig. 2, protection ring 32 protects edge 26a of the frustoconical member and its wearproof lining 29 from the wearing action of yarn F. As mentioned above, since edge 26a is freely received within the slot of the protection ring, the frustoconical member can be freely warped by the running yarn, which circumstance allows the braking action to be uniform.

Claims

A yarn-braking device for weft feeders provided with a weft-storing drum (12) having a delivery edge (12a) from which the yarn (F) is unwound to be fed to a textile machine, the yarn-braking device comprising a substantially frustoconical, hollow braking member (32) supported with its larger base facing the weft-storing drum and coaxially biased with its inner surface against said delivery edge (12a), characterized in that the edge (26a) of the larger base of the substantially frustoconical braking member (26) is lined with a protection ring (32) having an inner, circumferential slot (34) formed in the direction of the generatrices of the cone defined by the braking member, in which slot said edge (26a) is received.
The device of claim 1, characterized in that the height (H) of said inner, circumferential slot (34) is slightly greater than the thickness (S) of the braking member (26).
The device of claim 1 or 2, characterized in that said protection ring (32) is made of an elastomeric material.
The device of claim 3, characterized in that said elastomeric material is polyurethan.
The device of any of claims 1 to 5, characterized in that said slot (34) is defined between two parallel, circumferential lips (32a, 32b) engaging respective opposite faces of edge (26a), and in that the outer lip (32a) protrudes beyond the inner lip (32b).