IE41950B1 - A weft thread picking nozzle - Google Patents

Description

The invention relates to a weft thread picking nozzle of the type comprising a single stem hollow needle, having a closed tip at one end, an inlet at its other end for connection, in use, to a source of pressurised fluid and an outlet in part of its side wall adjacent the closed tip.

Nozzles of this type are Used in shuttleless looms and are located at successive locations from one end of the shed to the other so as to produce consecutively a plurality of fluid jets, which are each operative in a predetermined range of the weft picking trajectory and carry the weft thread through the shed.

Because of the needle-shape of said noz2les, they may readily enter between the warp threads into and out of the shed. Usually the nozzles are arranged to discharge jets of fluid into a guide tunnel formed within the shed by aligned, generally U-shaped recesses in the blades of the reed or by a separate comb-like member which is periodically moved into and out of the shed along with the nozzles.

A weft thread may thus be transported through the shed at a speed which is related to the velocity of the jets discharged from the weft-picking nozzles. A further determining factor is the direction of the fluid jets issuing from the individual nozzles. There is a certain direction of the fluid jets, at which the trans3 mission of the speed energy from the jet to the thread to be inserted is optimal. When the direction of the fluid jets deviates from this optimum direction, which is practically coincident with the central axis of the outlet of the nozzle, the transmission of the speed energy from the jet to the weft thread becomes less effective, as a result of which stagnation (i.e. weaving defects) may occur. The rate of discharge of fluid from the nozzles and hence the speed of the carrying fluid in the tunnel may in principle be increased by increasing the fluid pressure and the cross section of the outlet openings of the nozzles. An increase of the cross section of the outlet openings of the nozzles, however, entails more uncertainty with respect to the correctness of the direction of the fluid jets. Further the direction of each jet depends to a considerable extent on the pressure of the fluid supplied to the weft picking nozzles so that, with variations in pressure, the jet direction will also vary.

An object of the present invention is to provide an improved weft thread picking nozzle of the type initially referred to which, when used in a shuttleless loom, will enable the speed of transportation of the weft threads through the shed of the loom to be achieved.

With this object in view, according to the invention the outlet of a weft thread picking nozzle of the type referred to is composed of a plurality of elementary apertures which are individually of smaller crosssectional area than the hollow interior of the needle and are distributed at regular intervals both lengthwise and transversely of the hollow needle so as to form a continuous area pattern of apertures. 419 50 - 4 The composite outlet composed of these elementary apertures may be regarded as being equivalent to a single outlet opening provided with partitions which, in use, will subdivide the flow of fluid supplied from the interior of the hollow needle into a plurality of separate fluid jets which, as has been found by experiment, re-unite at a very short distance from the composite outlet of the nozzle so as to form, or at least behave as, a single coherent jet.

It has been found that the optimum direction of a fluid or gas jet discharged through such a composite outlet will be maintained when the sum of the cross-section areas of all the elementary apertures is substantially greater than the maximum cross-sectional area which the single outlet aperture of known weft thread picking nozzles of the type initially referred to can have without causing the direction of the jet discharged therefrom to diverge substantially from the optimum direction. Since the sum of the cross-sectional areas of all the elementary apertures of a weft thread picking nozzle according to the present invention can have such a relatively large value, a given jet velocity can be achieved-with fluid supplied at a pressure substantially lower than that required with known weft thread picking nozzles of the type initially referred to, which in turn enables the adverse effect of high fluid pressure on the direction of the jet to be obviated. Moreover, for any given supply pressure and any given pressure gradient, higher fluid velocities and hence higher weft speeds can be Obtained.

It has also been found that the composite outlet of the weft thread picking nozzle according to the invention has the effect of reducing the effect on the direction of the gas or liquid jet discharged therefrom of any inaccuracies in the shape of the portion of the wall surface leading from the straight part of the bore of the hollow needle to the outlet.

The invention will now be described by way of example with reference to the accompanying drawings, in which:Figure 1 is a longitudinal section of a needlelike weft-picking nozzle of a well-known construction.

Figure 2 is a similar section of a weft-picking nozzle embodying the present invention.

The weft-picking nozzle as shown in Figure 1 comprises a single stem hollow needle 1 which is provided with a single outlet aperture 2 in its side wall la adjacent the closed tip lb of the needle. The angle between the central axis I of the liquid or gas jet issuing through the aperture 2, when this weft-picking nozzle is in use, and the perpendicular to the londitudinal axis XX of the nozzle is indicated by^. Xn practice, the direction of the axis I deviates more or less from the axis III of the aperture 2, depending on the diameter d of that aperture and also on the accuracy of the curved portion 4a of the inner surface which leads from the main longitudinally straight portion 4 thereof to the aperture 2.

The weft-picking nozzle according to the embodiment of the invention shown in Figure 2 differs from the known weft-picking nozzle shown in Figure 1 in that its outlet 2’ consists of a plurality of elementary - 6 apertures which are individually of smaller cross-sectional area than the hollow interior of the needle 1.

The elementary apertures are distributed at regular closely spaced intervals both lengthwise and tranvers5 ely of the hollow needle 1 so as to form a continuous area pattern of apertures. The thickness of the partitions between the elementary apertures preferably does not materially exceed the diameter or cross-Seetional width of the elementary apertures. Again de10 notes the angle between the central axis I of the liquid or gas jet issuing from the Outlet 2' and the perpendicular to the longitudinal axis II of the nozzle.

Ah outlet comprising a plurality of elementary apertures as shown in Figure 2 may e.g. be produced by electro-erosion, The nozzle shown in Figure 2 may have its inlet end connected in known manner to a feel conduit located outside the shed of a loom provided with the said nozzle. Furthermore, the nozzle shown in Figure 2 may, if desi 20 red, be formed integrally with-a reed blade of the kind which is fontied with a generally U-shaped recess ard is designed to be fixed to a reed with this recess in alignment with like recesses in the other reed blades so that the aligned recesses in all the reed blades form a weft25 picking channel.

Claims (4)

1. CLAIMS:1. A weft thread picking nozzle of the type comprising a single stem hollow needle having a closed tip at one end, an inlet at its other end for connection, in use, to a source of pressurized fluid and an outlet in part of its side wall adjacent the closed tip, characterised in that the said outlet is composed of a plurality of elementary apertures which are individually of smaller cross-cross-sectional area than the hollow interior of the needle and are distributed at regular intervals both lengthwise and transversely of the hollow needle so as to form a continuous pattern of apertures .

2. A nozzle according to claim 1, characterised in that it is formed integrally with a reed blade of the kind which is formed with a generally U-shaped recess and is designed to be fixed to a reed with the said recess in alignment with like recesses in the other reed blades so that the aligned recesses in all the reed blades form a weft-picking channel.

3. A nozzle according to claim 1 to 2, characterised in that the elementary apertures are formed by electro-erosion.

4. A weft thread picking nozzle substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.