WO1994010075A1

WO1994010075A1 - Weft feeder

Info

Publication number: WO1994010075A1
Application number: PCT/EP1993/003086
Authority: WO
Inventors: Bruno Maina
Original assignee: Nuova Roj Electrotex S.R.L.
Priority date: 1992-11-05
Filing date: 1993-11-04
Publication date: 1994-05-11
Also published as: US5577536A; ITMI922544A1; KR950704173A; EP0668841B1; DE69304338D1; JPH08502943A; ES2093989T3; KR100310953B1; EP0668841A1; IT1258241B; DE69304338T2; ITMI922544A0; ATE141894T1

Abstract

Weft feeder from which the weft yarn (T) is unwound 'en défilé' from a reserve (R) on a drum (3), on the outlet end of which, upstream of an outlet yarn-guide (4), there acts a yarn braking device (1) comprising a frustoconical braking element (6) with varying flexibility and a cup support (8) with open base, the braking element comprising narrow tongues (7) placed side-by-side. In the braking element, said tongues join together, in the major circumference, into a band (6A) with a smooth and strictly continuous surface engaging the outlet end of the drum (3), while they are free and freely bear, in the minor circumference, against the inner periphery of the cup support (8). The braking element is connected to the cup support such that it can be deformed and/or perform limited movements in every direction. The outlet yarn-guide (4) is separate from the braking element (6) and is kept motionless, coaxial to the drum, while braking takes place.

Description

"WEFT FEEDER"

--00O00-- The present invention relates to devices to feed the weft yarn to machines making use thereof, in particular to a weft feeder for gripper or projectile looms having improved features.

It is well known in the art to feed the weft yarn to machines making use thereof, in particular looms, by means of feeder devices or "weft feeders": these are devices which are placed between the reel and the loom and whose function is to temporarily store the weft, facilitating its unwinding from the reel, and to subsequently supply it with preset optimum tension values to the loom picking members. The basic type of weft feeder which is in universal use today comprises winding the weft yarn in successive turns onto a drum, which is kept motionless, by means of a winding arm driven by an electric motor.

Means for controlling the quantity or reserve of weft yarn on the winding drum govern the rate and speed of rotation of the weft feeder motor as a function of the quantity of weft yarn unwound by the loom, ensuring the speed at which the weft is unwound from the reel is kept as uniform as possible. Where weft feeders are used on gripper or projectile looms, they are provided on their outlet side, for the purpose of imparting to the weft yarn fed to the loom a desired degree of tension, with braking means downstream of the drum on which the reserve is wound. Many of the known braking devices act directly on the outlet end of said drum and are found upstream of a weft feeder outlet yarn-guide provided in order to ensure that the weft yarn is correctly unwound "en defile". In many weft feeders the yarn braking devices used consist of a plurality of natural or synthetic bristles and are fixed to a support in the form of a closed ring which is carried by a bracket with the possibility of moving along the principle axis of the weft feeder, said plurality of bristles bearing, with a variable preloading that can be preset, by means of the adjustment of the axial position of said bracket, on the outer periphery of the weft feeder reserve winding drum. In other yarn braking devices, which act directly on the outlet end of the weft feeder drum, a braking element with a varying flexibility is used which comprises a plurality of narrow tongues placed side-by-side on a frustoconical surface. This braking element is mounted on a cup support with open base carried by a bracket of the weft feeder and whose position is adjustable along the axis of the drum. An example of the latter yarn braking devices which has been widely used and which comprises tongues in the form of metal drop-wires, is illustrated in European Patent no. 49,897 belonging to the Applicant.

However, even though the conditions under which the weft yarn is inserted into the loom have been improved in the weft yarn feeders used in the yarn braking devices mentioned above, the problem of controlling the tension of the weft yarn fed to the loom at an optimum value has not been fully or effectively resolved. This problem becomes particularly troublesome during the weft insertion cycle in gripper looms in which the weft yarn is switched mid-shed, during which cycle the yarn must be kept at a high tension as it is gripped by the carrier gripper on entering the shed and as the end of the yarn is passed from the carrier gripper to the puller gripper, mid-shed.

So, in the known yarn braking devices discussed above, it is precisely the tendency which the weft feeders have of allowing the tension of the yarn when switched to fall below the requisite values which con¬ stitutes the drawbacks of such devices. These drawbacks are overcome by increasing the preset tension in order to maintain a sufficiently high tension at the switch-over point. However, this means increasing the maximum value of the tension when that given by the inertia of the yarn at the time of maximum acceleration of the grippers, before and after the switch-over, is added to the preset tension produced by the breaking action.

The resulting tension peaks are clearly not desired since they cause high stresses in the weft yarn, which could easily lead to the yarn breaking.

There is clearly a need, therefore, for weft feeders which, by keeping the tension of the weft yarn being fed to the loom as low as possible, in order for the loom to operate correctly, eliminate the damaging tension peaks which currently occur in said yarn (and obviously also the similarly damaging drops in tension) , simultaneously ensuring the best operating conditions with respect to the gripping and switching of the weft yarn.

This need is fully satisfied by the present invention which relates to a device to feed the weft yarn to machines making use thereof, in particular a weft feeder for gripper or projectile looms - of the type in which the weft yarn being fed to the loom is unwound "en defile" from a weft yarn reserve wound on a drum, on the outlet end of which, where a first weft yarn deviation takes place, there acts a yarn braking device, upstream of an outlet yarn-guide, where a second weft yarn deviation takes place, and in which the yarn braking device, centred on the drum axis and adjustable along the drum, is of the type comprising a frustoconical braking element with varying flexibility, carried by a support in the form of a cup with open base, the frustoconical surface of the braking element comprising a plurality of narrow tongues, placed side-by-side substantially along the generating lines of said surface, said tongues being reciprocally connected along the major circumference and being free along the minor circumference - characterized in that, in said braking element, said tongues join, in the region of the major circumference, into a band with a smooth and strictly continuous surface engaging the outlet end of the drum, while they freely bear, in the region of the minor circumference, against the inner periphery of the cup support, the braking element being connected to the cup support through at least two of said tongues and through means allowing it to be deformed and/or to perform limited movements in every direction with respect to said cup support; and in that said outlet yarn-guide is separate from the braking element of the yarn braking device and is kept motionless, coaxial to the drum, while braking takes place.

In this weft feeder the means to connect the braking element of the yarn braking device to its cup support comprise a plurality of pins, emerging from the support and engaging into slots formed in the free ends of said tongues, as well as a ring fixed on the free ends of said pins.

The tongues of the braking element of the yarn braking device of the weft feeder are positioned along the generating lines of the frustoconical surface of the braking element or are positioned inclined and/or par¬ tially undulated with respect to said generating lines.

The band with a strictly continuous surface engaging the outlet end of the drum of the frustoconical braking element of the yarn braking device may be advantageously formed by applying onto the inner surface of said element, in the region of its major circumference, a frustoconical stiffening ring which increases the varying flexibility of said braking element. The invention will now be described in greater detail, by way of example, with reference to a preferred embodiment thereof, represented in the appended drawings, in which:

Fig. 1 shows a lateral overall view of the weft feeder according to the present invention; and

Fig. 2 is a detailed perspective view, in partial section, of the yarn braking device and of other parts connected with the invention of the weft feeder of Fig. 1. Fig. 1 shows the weft feeder AT according to the invention, fed with yarn F from a bobbin B or reel and used to feed said yarn as weft yarn T to a gripper or projectile loom (not shown) . In a known manner, in this feeder, a reserve R of yarn F is wound by a winding element 2 onto the drum 3 of the weft feeder in the form of turns. The weft yarn T is unwound "en defile" by the loom from said reserve R, and is guided by an outlet yarn-guide 4, after having been subjected to a braking action in the region of the free end of the drum 3. The yarn-guide 4 is supported by a bracket 5, along the axis of the drum 3 and downstream from it. The quantity of reserve yarn R and the position of the yam-guide 4 along the axis of the drum 3 can be adjusted by varying the speed and the periods of operation of the winder 2 and the position of the bracket 5 respectively.

The braking action on the weft yarn T at the outlet is produced, in the weft feeder described above, by means of a yam braking device 1 comprising a braking element with a frustoconical surface 6 which for this purpose engages tangentially with the end of the drum 3 at its periphery.

The braking element 6 of the weft feeder according to the invention comprises a plurality of narrow tongues 7, placed side-by-side so as to form a frustoconical surface and orientated essentially along the generating lines of this surface. The tongues 7 are preferably metal drop-wires, though the use of other materials, whether natural or artificial, for example synthetic plastic materials, is by no means excluded, as long as these materials have a high flexibility. The tongues (or drop-wires) 7 are reciprocally connected along the major circumference of the frustoconical surface of the element 6, where they join into a broad¬ band 6A with a strictly continuous surface, engaging the dome of the drum 3, and are free in the region of the minor circumference, where they are mounted on the inner periphery of a cup support 8 with open base. The outlet yarn-guide 4 can be separate from the cup support 8 of the yarn braking device 1 or may be incorporated into it. It may additionally be fixedly mounted on a bracket, e.g. 5, adjustable along the axis of the feeder and of the drum 3, or it may be mounted so that it can move on said bracket, adjustable along the same axis, the bracket itself being fixed to the weft feeder.

In the embodiment illustrated, the yarn-guide 4 is incorporated in the open base of the cup support 8 of the yarn braking device 1, such that the base of the cup support 8 and the outlet yarn-guide 4 substantially coincide and are carried by the same bracket 5. By varying the position of the bracket, the distance between the drum 3 and the yarn-guide 4 and between the drum 3 and the yarn braking device 1 is also varied, as is therefore the braking action exerted by the latter on the outlet end of said drum.

As clearly shown in Fig. 2 and still according to the invention, the braking element 6 is connected to the cup support 8 through only some of said tongues or drop- wires 7 and through means allowing it to be deformed and/or to perform limited movements in every direction with respect to said cup support. More precisely the cup support 8 carries on its periphery a plurality of emerging pins 9 engaging into slots 10 formed in the free ends of some of the drop- wires 7, as well as a locking ring 11 which is fixed, for example by pressure or by welding, onto the free ends of said pins 9, after the pins 9 have been inserted in the slots 10. The slots are shown in Fig. 2 as being obtained by joining the free ends of pairs of the side-by-side drop-wires 7 which form the braking element 6, but they could also be formed in a different manner (for example directly as slots in the free ends of some, uniformally spaced, of the drop-wires 7 which form the braking element 6) .

As has already been described, the structure of the braking element 6 means that the tongues 7 are positioned substantially along the generating lines of its frustoconical surface. Fig. 1 illustrates straight tongues 7, arranged exactly along said generating lines, whereas Fig. 2 shows tongues 7 in the form of drop-wires which are positioned inclined and/or partially undulated with respect to the generating lines of the conical surface of the braking element 6.

As have already been described, the braking element 6 bears against the outlet end of the drum 3 via its band 6A in order to exert a braking action on the yarn F which is unwound "en defile" from the drum 3 towards the outlet yarn-guide 4 of the weft feeder. The band 6A must ensure that contact between the drums 3 and the yarn F is as uniform as possible in order to prevent harmful peaks or drops in tension in the yarn itself. For this purpose the surface of the band 6A is smooth and strictly continuous, without any significant interruption. Therefore, the band 6A can be made as one piece with the tongues 7 forming the braking element 6, or it can be applied in various ways to the inside of the end of said element 6 having the greatest circumference. In this second case - illustrated in Fig. 2 (in which the representation of the band 6A is interrupted at the bottom) - it may prove expedient to form the band 6A as a drawn metal ring which, by stiffening said end of the braking element 6, advantageously increases the varying flexibility of this element.

The specific configuration described above of the yarn-braking device 1 - and principally the mounting thereof which enables the braking element 6 to be greatly deformed and to be moved to a moderate degree in all directions on the cup support 8 (namely a mounting in the manner of a universal joint which guarantees complete freedom) , the varying flexibility of the structure of the braking element and the continuity of the surface of its band 6 engaging with the drum 3 - mean that said device is best adapted in the area of tangency with the drum 3 to the deformations caused by the passage of the weft yarn. The features of the yarn-braking device 1 described above are combined:

- with the presence of an outlet yarn-guide 4, which is separate from the braking element 6 of said device 1 and kept motionless while braking takes place, which the yarn F reaches passing freely through the space within the braking element 6 without being deviated therein (in fact the weft yarn T only undergoes a first deviation in the region of the braking zone, at the outlet end of the drum 3 and a second deviation in the region of the outlet yarn-guide 4) ;

- and with the fact that the position of said yarn-guide 4 and of the cup support 8 of the yarn braking element 1 can be adjusted along the axis of the drum 3 (so as to graduate the braking action) .

All this means that the weft feeder according to the invention outstandingly solves - using means which are very reliable and which do not require maintenance or frequent replacement - the problem of eliminating damaging peaks or drops in the tension of the weft yarn or at least reduces this phenomenon to a level which is acceptable as regards the practical requirements of weaving, even on the most technologically advanced looms.

The underlying solutions which form the subject of the invention may, of course, be adapted to the individual requirements of the weft feeders and of the various machines to which they are applied, by making adjustments of a design nature, such as in the choice of materials, the number and the design of, and the distance between, the tongues 7 which form the braking element 6, the method and materials used to make the band 6A of this element, the way in which the braking element 6 and its cup support 8 are joined at the construction stage, the structure and mounting of the outlet yarn-guide 4, and the structure and mounting of the cup support 8. With particular reference to the last two items (as has already been seen the cup support of the yarn braking device and the outlet yarn-guide may be separate or one may be incorporated inside the other) , an interesting and alternative solution to that illustrated would consist in mounting the cup support of the yarn braking device so that it can move with respect to a bracket of the weft feeder, which bracket is fixed to said weft feeder, with the possibility of adjusting the position of said support along the axis of the drum, for example using screw means carried on said bracket which are coaxial to the axis of the weft feeder drum.

All the above adjustments and any other embodiment which is a variant of the weft feeder described and illustrated will, of course, be encompassed by the scope of the present invention.

Claims

1) Device to feed the weft yarn to machines making use thereof, preferably weft feeder for gripper or projectile looms - of the type in which the weft yarn being fed to the loom is unwound "en defile" from a weft yarn reserve wound on a drum, on the outlet end of which, where a first weft yarn deviation takes place, there acts a yarn braking device, upstream of an outlet yarn-guide, where a second weft yarn deviation takes place, and in which the yarn braking device, centred on the drum axis and adjustable along the drum, is of the type comprising a frustoconical braking element with varying flexibility, carried by a support in the form of a cup with open base, the frustoconical surface of the braking element com- prising a plurality of narrow tongues, placed side-by- side substantially along the generating lines of said surface, said tongues being reciprocally connected along the major circumference and being free along the minor circumference - characterized in that, in said braking element, said tongues join, in the region of the major circumference, into a band with a smooth and strictly continuous surface engaging the outlet end of the drum, while they freely bear, in the region of the minor circumference, against the inner periphery of the cup support, the braking element being connected to the cup support through at least two of said tongues and through means allowing it to be deformed and/or to perform limited movements in every direction with respect to said cup support; and in that said outlet yarn-guide is separate from the braking element of the yarn braking device and is kept motionless, coaxial to the drum, while braking takes place.

2) Weft feeder as in Claim 1) wherein the cup support of the yarn braking device is fixedly mounted onto a bracket of the weft feeder, the position of said bracket being adjustable along the axis of the weft feeder drum.

3) Weft feeder as in Claim 1) , wherein the cup support of the yarn braking device is mounted on a bracket, movable with respect thereto, the bracket being fixed to the weft feeder, with the possibility to adjust the position of the cup support with respect to said bracket along the axis of the weft feeder drum. 4) Weft feeder as in Claim 1) , wherein the position of the outlet yarn-guide along the drum axis is adjustable.

5) Weft feeder as in Claim 1) , wherein the position of the outlet yarn-guide along the drum axis is fixed.

6) Weft feeder as in Claims 1) to 5) , wherein the means to connect the braking element of the yarn braking device to its cup support comprise a plurality of pins, emerging from the periphery of said support and engaging into slots formed in the free ends of said tongues, as well as a ring fixed on the free ends of said pins.

7) Weft feeder as in Claim 6) , wherein said slots are obtained by joining the free ends of pairs of the side-by-side tongues which form the braking element of the yarn braking device.

8) Weft feeder as in Claim 6) , wherein said slots are formed into the free end of some of the tongues forming the braking element of the yarn braking device.

9) Weft feeder as in Claims 1) to 8) , wherein the tongues of the braking element of the yarn braking device are positioned along the generating lines of the frusto¬ conical surface of said braking element.

10) Weft feeder as in Claims 1) to 8) , wherein the tongues of the braking element of the yarn braking device are positioned inclined and/or partially undulated with respect to the generating lines of the frustoconical surface of said braking element.

11) Weft feeder as in Claim 1) , wherein the outlet yarn-guide is incorporated into the base of the cup support of the yarn braking device, and its position along the drum axis can be adjusted together with the position of said support and of said device.

12) Weft feeder as in Claim 1) , wherein the outlet yarn-guide corresponds to the open base of the cup support of the yarn braking device.

13) Weft feeder as in Claims 1) to 12) , wherein the smooth and strictly continuous band engaging the outlet end of the weft feeder drum of the frustoconical braking element of the yarn braking device, is formed by applying onto the inner surface of said element, in the region of its major circumference, a frustoconical stiffening ring.

14) Weft feeder as in Claim 1) , wherein said frustoconical stiffening ring is a metal ring obtained by drawing.