Weft feeder for fluid jet looms

Abstract: In a weft feeder for fluid jet looms - of the type measuring the weft yarn lengths being inserted into the loom shed (measuring weft feeder), comprising an electric motor causing the rotation of a winding arm, a drum (3) held stationary around which said arm winds up the yarn (4) into even turns, forming a weft warn reserve the length of which is controlled by means of suitable sensors, and a yarn stopping device (8) comprising a rod (9) engaging and stopping the yarn (4) at the outlet of the feeder, said rod (9) being movable between a withdrawn rest position and a projecting yarn stopping position in which its end moves into a cavity (10) formed for the purpose on the drum periphery, close to the free end thereof - into said drum cavity there is mounted a plurality of bristles (12) positioned transversally to the rod (9) of the yarn stopping device, so that said rod (9) may engage said plurality of bristles (12), crossing it at least partially, when taking up its projecting position to stop the weft yarn (4).

Description: The present invention concerns improvements in weft feeders for fluid jet looms, of the type - apt to measure the weft yarn lengths being inserted into the loom shed - known as "measuring weft feeders". As known, a weft feeder of this type (as shown for example in CH-A- 670 263) comprises an electric motor which causes the rotation of a yarn winding arm, and a drum held stationary around which said arm winds up the yarn into even turns, forming a weft yarn reserve the length of which is controlled by means of suitable sensors. The loom nozzle, provided to launch the weft yarn into the loom shed, draws from the weft feeder drum the weft yarn length required for each weft insertion. Said length is measured and controlled by the weft feeder counting the number of unwound turns by suitable means. As soon as the yarn at the outlet of the weft feeder, to be launched into the loom shed, has reached the predetermined length, it is stopped on the drum by means of a device comprising a rod apt to engage the yarn at the outlet of the feeder, said rod being movable between a withdrawn rest position and a projecting working position in which the end of the rod moves into a cavity formed for the purpose on the drum periphery, close to its free end, so as to stop the weft yarn by engaging the same as it unwinds from the drum. Preferably, the weft yarn stopping device is an electromagnetic device, wherein said rod projects from a movable core, which comprises a head of ferromagnetic material subject to the contrasting actions of at least an electromagnetic coil and of a return spring, allowing to move said rod alternatively into the projecting yarn stopping position and into the withdrawn rest position. The rod stopping device of measuring weft feeders is, in most cases, quite valid and reliable. However, it sometimes happens that the weft yarn may slip away under the rod of the stopping device and move beyond the same, by wedging into the drum cavity housing the end of said rod and passing between the rod and the bottom of said cavity without stopping, or stopping with some delay, which irreparably alters the exactness of the measurement and causes even serious inconveniences to the working of the weft feeder and of the loom. This phenomenon mostly occurs with yarns having a strong twist or a high rigidity, as they are being cut by the loom shears after weft insertion. It is mainly determined by the sudden change in weft yarn tension when cutting takes place, which causes longitudinal and transversal oscillations between the yarn stopping point on the measuring weft feeder and its cutting point on the loom. Said oscillations cause jumping of the yarn, which thus wedges in between the end part of the stop rod and the bottom of the drum cavity, without stopping. Alternatively, "In document CH-A- 670 263, the weft thread is prevented from slipping out of the cavity by grooves or a brush mounted at the bottom of the cavity, the brush bristles being in line with the rod of the yarn stopping device." a small space is provided for this purpose, between the end of the stop rod and the bottom of the drum cavity, by forming the rod limit stop means directly inside the structure of the electromagnetic stopping device, this solution being more apt to guarantee the working of said stopping device. When the weft yarn slips away, passing under the stop rod, there is of course a measuring error which generally produces a weft insertion longer than required or, in the case of a loom working with several colours, the insertion of a weft length in the successive beating up together with the correct insertion of a different colour. Attempts have been made in the past to overcome this drawback, by providing for the free end of the stop rod to come in contact with an element positioned at the bottom of the drum cavity, said element having to be sufficiently elastic, so as not to form a limit stop, and sufficiently resistant to rubbing wear, caused both by the yarn trying to slip away and by the rod hitting against said yarn. Nevertheless, by adopting this system, it is on one hand difficult to positively prevent any rebounds of the stop rod - which are obviously harmful from many points of view - and, on the other hand, it has turned out impossible to realize an element against which the rod should stop, being so strong as not to require replacement after short periods of use of the weft feeder. The present invention now proposes a fully original solution to this problem, which is besides highly satisfactory as seen hereinafter. Said solution - applied to a measuring weft feeder of the aforementioned type - consists in mounting, into the drum cavity designed to house the end of the rod of the weft yarn stopping device, a plurality of bristles which are positioned therein transversally to said rod, so that this latter may engage said plurality of bristles, crossing it at least partially, when taking up its projecting position to stop the weft yarn. Preferably, said plurality of bristles is formed as a brush, with the bristles mounted projecting, substantially parallel to the drum axis. The invention is now described in further detail, with reference to the accompanying drawings, which illustrate a preferred embodiment thereof, and in which: Fig. 1 is a lateral view of a measuring weft feeder, onto which the invention has been applied; Fig. 2 is a lateral view, on an enlarged scale, of the yarn stopping device of said weft feeder and of the drum cavity housing the end of the yarn stop rod, said cavity comprising the arrangement according to the invention; Figs. 3 and 4 are section views, respectively along lines III-III and IV-IV of fig. 2; and Fig. 5 is a section view along line V-V of fig. 3; figs. 3 to 5 showing in further detail the arrangement according to the invention. Figure 1 shows diagrammatically a measuring weft feeder to feed the weft yarn to fluid jet looms. In known manner, said weft feeder houses into its body 1 an electric motor causing the rotation of a winding arm 2, and comprises a drum 3 held stationary around which said arm 2 winds up the weft yarn 4 into even turns, forming a reserve 5 controlled by sensors 6, the length of said yarn turns being adjustable by changing the radial position of columns 7 which allow to vary the diameter of the drum 3. In this measuring weft feeder the weft yarn 4 being fed to the loom is stopped after a predetermined length thereof has been withdrawn. This operation is accomplished by the yarn stopping device 8, when its rod 9 is moved into the projecting position and introduced into the cavity 10 provided therefor on the periphery of the drum 3, close to its free end, to thereby engage and stop the yarn 4. The yarn stopping device is preferably an electromagnetic device comprising a body fixed to the measuring weft feeder, which houses at least one electromagnetic coil, a spring and a movable core provided with a ferromagnetic head apt to respond to the contrasting actions of said coil and of said spring, the yarn stop rod 9 projecting from said movable core. The yarn stopping device could also have different characteristics (nor does it necessarily have to be an electromagnetic device). In the drawings, the yarn stopping device 8 is shown in a working position, with the rod 9 penetrating through a slit 11 into the cavity 10 provided therefor on the drum 3. According to the invention, into the cavity 10 there is mounted a plurality of natural or artificial bristles 12, positioned in the form of a brush transversally to the rod 9 which, when moving into a projecting yarn stopping position, engages said bristles 12 and crosses them at least partly. The plurality of bristles 12 is preferably mounted - as shown - with the bristles projecting from a support body 13 and extending parallel to the axis of the drum 3 (and thus substantially perpendicular to the stop rod 9). This simple arrangement positively prevents the forming of a space to allow yarn passage - even when the yarn undergoes irregular movements or sudden tension changes - while housing the end of the yarn stop rod without opposing any resistance (and thus without wearing, or causing even slight undesirable rebounds of said stop rod). The material forming the bristles is preferably artificial or obtained from an animal source, but it could also be of mineral or vegetal origin. Even if the arrangement preferred at present is that shown in the drawings, with the bristles positioned parallel to the weft feeder axis, it is also possible to mount said bristles in a different position, for instance transversal to or inclined in respect of said axis. It is deemed that the proposed solution is apt to solve most satisfactorily the problem being faced. In fact: the actual nature of the bristles - already used since long, in the construction of weft feeders, as brake elements for adjusting weft yarn tension - provides a high resistance to wear caused by contact with the yarn as well as with the stop rod; the brush arrangement of the bristles allows a soft and efficient penetration of the yarn stop rod, preventing the forming of spaces for yarn passage beneath the same; the bristles, besides causing no rebounds of the stop rod, prevent its end from getting damaged through impact; the high elasticity of the bristles allows slight oscillations of the drum about its axis, without causing any damage either to the stop rod or to the bristles.

Claims: Weft feeder for fluid jet looms, of the type - apt to measure the weft yarn lengths being inserted into the loom shed (measuring weft feeder) - comprising an electric motor causing the rotation of a winding arm (2), a drum (3) held stationary around which said arm (2) winds up the yarn (4) into even turns, forming a weft yarn reserve the length of which is controlled by means of suitable sensors (6), and a yarn stopping device (8) comprising a rod (9) apt to engage and stop the yarn at the outlet of the feeder, said rod (9) being movable between a withdrawn rest position and a projecting yarn stopping position in which its end moves into a cavity (10) formed for the purpose on the drum periphery, close to the free end thereof, characterized in that, into said drum cavity (10) there is mounted a plurality of bristles (12) positioned transversally to the rod (9) of the yarn stopping device (8), so that said rod (9) may engage said plurality of bristles (12), crossing it at least partially, when taking up its projecting position to stop the weft yarn (4). Weft feeder as in claim 1), wherein said plurality of bristles (12) is formed as a brush. Weft feeder as in claim 1), wherein the bristles of said plurality of bristles are mounted projecting from a suitable support body (13). Weft feeder as in claim 1), wherein the bristles of said plurality of bristles (12) are substantially parallel to the drum axis. Weft feeder as in claim 1), wherein said yarn stopping device (8) is an electromagnetic device.

Inventors: MAINA BRUNO, MAINA, BRUNO
Applicants: ROY ELECTROTEX SPA, ROJ ELECTROTEX S.P.A.
Application year: 1991
Main classification: D03D47
IPC codes: D03D51, D03D47