GB2073791A

GB2073791A - Weft Picking Device of Air Jet Loom

Info

Publication number: GB2073791A
Application number: GB8110968A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1980-04-12
Filing date: 1981-04-08
Publication date: 1981-10-21
Also published as: CH650538A5; JPS56144248A; IT8148252A0; CS229662B2; JPS6032732B2; FR2480317A1; DE3113594A1; GB2073791B; FR2480317B1

Abstract

A confusor for an air jet loom, comprises a plurality of teeth (3) with respective straight air guide openings (4) through which a weft yarn (12) from a weft inserting nozzle is picked, each tooth having an exit slot (5) through which the weft yarn passes on beat-up and being so spaced from adjacent tooth as to cancel air stream fractions leaking through the slots (5) by air stream fractions leaking through the spaces between the teeth, thereby achieving air saving and preventing the weft yarn from fluttering and passing out of the slots, during the weft picking. Dimensions of the confusor are given. <IMAGE>

Description

SPECIFICATION Weft Picking Device of Air Jet Loom This invention relates to an improvement in a weft picking device of an air jet loom, of the type having a weft inserting or main nozzle and a plurality of auxiliary nozzles wherein weft picking is accomplished by carrying the weft yarn from the weft inserting nozzle mainly under the influence of the air jets from the auxiliary nozzles.

In connection with weft picking in air jet looms, it is well known that there are mainly two kinds of weft picking devices as discussed hereinafter. One (referred to as "the first conventional weft picking device" hereinafter) of them is as follows: an air jet ejected from a main nozzle is converged into the axis of a weft guide channel defined by a plurality of tapered air guide openings of successively located air guide members which are relatively closely aligned in the direction of weft insertion, so that an air stream.formed in the weft guide channel is introduced toward a loom side opposite to the main nozzle.

A weft yarn injected from the main nozzle together with the air jet is carried by the thus formed air stream to accomplish the weft picking. In this case, the air stream formed in the weft guide channel may be enhanced by the air jet from an auxiliary nozzle positioned between two adjacent air guide members which are located near the loom side opposite to the main nozzle, if necessary.

Another (referred to as "the second conventional weft picking device" hereinafter) of them is as follows: a plurality of U-shaped air guide members are relatively widely spaced in alignment along the direction of weft picking in such a manner as to close the three ways of a weft guide channel, and additionally a plurality of auxiliary nozzles are located at suitable intervals along the weft guide channel to angularly eject air jets toward the inner surfaces of the U-shaped air guide members, in which the air jet from the main nozzle serves only to inject or push out the weft yarn into the weft guide channel, whereas the air jets from the auxiliary nozzles serve to carry the thus injected weft yarn throughout the weft guide channe!.In this device, when the weft yarn injected from the main nozzle reaches the vicinity of an auxiliary nozzle which is positioned nearest the main nozzle, the auxiliary nozzle ejects an air jet to blow away the weft yarn toward the loom side opposite to the main nozzle, and such an air jet itself passes out of the weft guide channel through the alignment clearances of the air guide members, so that the weft yarn is carried within a predetermined distance along the bottom sections of the inner surfaces of the U-shaped air guide members. Such an action is in turn taken over to the succeeding auxiliary nozzle to accomplish the weft picking.

As will be apparent from the above discussion, with the first conventional weft picking device, since the weft guide channel is formed by the radially almost closed air guide openings of the successively located air guide members, the air jet from the main nozzle can be used to carry the weft yarn to the loom side opposite to the main nozzle. However, the air stream caused by the air jet from the main nozzle is successively subjected to converging actions due to the tapered air guide openings, in which flow resistances due to the convergence of the air stream are accumulated. Additionally, air leak through alignment clearances of the air guide members cannot be avoided while its amount is less.As a result, the flow speed of the air stream gradually decreases in the weft guide channel therefore the first conventional weft picking device is not considered suitable for weaving a wide fabric.

With the second conventional weft picking device, air amount saving in the main nozzle can be achieved. Additionally, the carrying action of the weft yarn is allotted to a plurality of the auxiliary nozzles and therefore this second conventional weft picking device is suitable for weaving a wide fabric. However, the air stream for carrying the weft yarn is formed along the bottom section of the inner surface of each U-shaped air guide member, in which the flow speed of the air stream rapidly decreases upon receiving flow resistance from the air guide member inner surface bottom section. As a result, the overall flow speed of the air stream in the weft guide channel is lowered and accordingly the advancing direction of the weft yarn becomes unstable, thereby causing a failed weft picking, for example, due to being caught in the clearance between the air guide members.Furthermore, the air jets from the auxiliary nozzles unavoidably pass out of the weft guide channel still keeping velocity energy as discussed above, and additionally air reflected on the inner surface of the U-shaped air guide members is diffused or dissipated, so that such air cannot be used for carrying the weft yarn. Therefore, it is necessary to increase the number of the auxiliary nozzles to compensate air by an amount corresponding to the above dissipated air, which necessarily increases the amount of required compressed air.

In view of the above, it has been already proposed to solve the problems encountered in the above-mentioned second conventional weft picking device by replacing its air guide members with the air guide members used in the above-mentioned first conventional weft picking device, on the basis of the idea wherein the carrying action of the weft yarn is accomplished mainly under the influence of the air jets from the auxiliary nozzles as disclosed in United States patent application No. 149,083 entitled "Weft Picking Device of Air Jet Type Weaving Loom." A weft picking device of an air jet loom, according to the present invention comprises a plurality of air guide members aligned in the direction of weft picking.The air guide members are formed therethrough with respective straight air guide openings without any taper, which air guide openings constitute a weft guide channel through which a weft yarn from an weft inserting nozzle is picked. Each air guide member is formed with a slit through which the weft yarn passes out of the air guide opening.

Each air guide member is spaced from adjacent air guide members so as to cancel the leakage of an air stream fraction through the air guide member slit with the leakage of an air stream fraction through the spaces between the air guide members so that the weft yarn is prevented from flying out of the weft guide channel through the air guide member slit.

With this arrangement, it has becomes possible to considerably decrease the diameter of the air guide opening of each air guide member in order to achieve great air saving, preventing the weft yarn from fluttering and flying out of the weft guide channel during the weft picking.

The features and advantages of the weft picking device of an air jet loom according to the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate like parts and elements, and in which: Fig. 1 is a front elevation of a preferred embodiment of a weft picking device of an air jet loom, in accordance with the present invention; Fig. 2 is an enlarged cross-sectional view taken in the direction of arrows substantially along the line Il-li of Fig. 1; Fig. 3 is a transverse sectional view of the essential part of the weft picking device of Fig. 1, illustrating a state of weft picking; and Fig. 4 is an illustration showing an experimental result obtained by one of various experiments which were carried out in the process of reaching the present invention.

To facilitate understanding the present invention, a brief reference will be made to the result of experiments conducted by the inventors for the purpose of decreasing the amount of pressurized air required for weft picking on the basis of the weft picking device disclosed in United States Patent Application No. 149,083. The experiments discussed thereinafter exhibit the effect of the decreased diameters of air guide openings of air guide members.The experiments were so conducted that a weft yarn was injected from a main nozzle into a weft guide channel defined by the air guide opening of each air guide member successively aligned along the direction of weft insertion, decreasing the average diameter D' of the tapered (Tp:taper) air guide opening A of each air guide member shown in Fig. 4 as 18 mm, 16 mm, and 14 mm under the experimental conditions where: Taper (Tp) angle (relative to the axis of the weft guide channel on cross-section containing the axis, 7 degrees Air guide member thickness 2.9 mm Distance between air guide members 0.8 mm Auxiliary nozzles Nozzle opening diameter 1.0 mm Alignment pitch 10 cm Air ejection direction 12 degrees (relative to the axis of the weft guide channel).

In the above-mentioned experiments, good weft pickings were accomplished even on the variation of the average diameter of the air guide opening of each air guide member. However, further experiments revealed that when the average diameter D' was decreased to 12 mm, slight fluttering of the moving weft yarn was caused so that the weft yarn looked to be caught by a slit B; and when the average diameter D' was further decreased to 10 mm, the leading end of the weft yarn flew out of the slit B; by which the weft picking became impossible. The line L shown in Fig. 4 indicates the locus of the weft yarn leading end which was sketched on observation from the loom side opposite to the main nozzle when the weft yarn fluttering occurred.

Studying the above-discussed fluttering of the weft yarn leading end, the effect of the taper (Tp) formed on the surface of the air guide opening of the air guide member is considered as a cause of the weft yarn leading end fluttering. Since the tapers (Tp) are inherently formed to successively converge the air stream passing through the successively aligned air guide openings A, it is considered as a matter of course that the air stream passes throughout the weft guide channel repeating its contraction and expansion. It will be understood that if the air guide opening diameter D' decreases, the crosssectional area of the air guide opening greatly decreases in relation to the square of the increased amount of the diameter D'. Accordingly, it seems that at the air guide opening diameter of 1 2 mm in the above-mentioned experiments, the effect of repeating contraction and expansion of the air stream spreads over all ranges of the weft guide channel, thereby causing the fluttering of the free end or leading end of the moving weft yarn in the weft guide channel.

For the purpose of comparison with the above-mentioned experimental results, further experiments were next conducted under the above-mentioned experimental conditions with the exception that a straight air guide opening without the taper (Tp) was used in place of the tapered air guide opening A which straight air guide opening of each air guide member is defined by a generally circular inner surface which is perpendicular to a plane parallel with each air guide member as indicated by the reference numeral 4 in Fig. 3.These experiments revealed that when the average diameter of the air guide opening was the above-described values larger than 12 mm, the fluttering of the weft yarn greatly decreased; when the same diameter was 12 mm, the action of the weft yarn was fairly good; when the same diameter was 10 mm, the weft picking was possible while the leading end of the weft yarn appeared to fly out of the weft guide channel; and when the same diameter was 7 mm, the leading end of the weft yarn flew out of the weft guide channel so that weft picking became impossible.

A further consideration on this weft yarn flying out phenomena have revealed the following facts: Although the diameter of the air guide opening of each air guide member can be freely decreased, the width E of the slit B cannot be decreased since the weft yarn passes through this slit B. Accordingly, the ratio in cross-sectional area between the slit B and the air guide opening A greatly increases with the decrease in diameter of the air guide opening A of each air guide member. This increases the ratio of the air stream fraction passing out of the air guide opening through the slit B, so that the leading end of the weft yarn flies out of the weft guide channel through the slit B under the influence of the abovementioned air stream fraction passing out through the slit B.Additionally, it is assumed that the relative increase in the above-mentioned passing out air stream fraction is larger than that in the air stream fraction which passes out through the alignment clearances of the air guide members due to omitting the taper (Tp) of the air guide opening of each air guide member.

The above led to the idea wherein, in order to cancel the harmful air stream fraction passing out through the slit B, it was effective to increase a suitable amount of air stream fraction got out through the alignment clearance of the air guide members. On the basis of this idea, the experiments were further so conducted that each alignment clearance of the air guide members was increased under the experimental conditions where air guide member thickness is 2.9 mm; auxiliary nozzle alignment pitch is 10 mm; and auxiliary nozzle air ejection direction is within a range from 12 degrees to 15 degrees relative to the axis of the weft guide channel. The result of the experiments are shown in Table 1 in combination with the result of the above-mentioned experiments regarding the air guide members with the straight air guide openings without any taper Tp.

Table 1

Airguide opening Distance (mum) between A AuxiliarynozzSe opening diameter (mum) air guide members diameter (mum) Weft picking state 12 0.8 1.0 Fairly good 10 0.8 1.0 Weft picking possible though seemed to fly out through seemed to fly out through 7 0.8 1.0 the slit B 10 1.6 1.0 Weft picking impossible to be dragged toward the slit B 10 1.6 1.2 good 10 1.2 1.2 7 1.6 1.0 excelient 7 1.6 1.2 6 1.2 1.0 Weft picking possible though the weft yarn contacted air guide opening inner surface Air guide member thickness 2.9 mm Auxiliary nozzle alignment pitch 10 cm air ejection direction 12-1 5 degrees The total review of the experimental results discussed hereinbefore has led to the following conclusion:In the weft picking device constituted by combining the tapered air guide openings of each air guide members, the main nozzle, and the auxiliary nozzles, the lower limit of the air guide opening diameter exists in the vicinity of 12 mm. In order to further decrease the air guide opening of each air guide member accomplishing good weft picking, it is necessary to omit the taper Tp of the air guide opening and additionally to so set the width of each alignment clearance between the air guide members that a suitable amount of air stream fraction leaks therethrough, in which the lower limit of the diameter of the air guide opening of each air guide member exists in the vicinity of 6 mm.

It will be appreciated that the present invention has been envisaged throughout the above discussed processes and on the basis of the before-mentioned first conventional weft picking device wherein an air jet from the main nozzle is guided as far as possible throughout the weft guide channel constituted by the air guide openings which are defined by a series of radially almost closed air guide members, and the air stream due to the air jet from the main nozzle is enhanced by the air jet from the auxiliary nozzle near the weft guide channel, thereby intending to further same air amount consumed for weft picking.

In view of the above, in the weft picking device according to the present invention, for the purpose of decreasing the diameter of the air guide opening of each air guide member to an extent where weft picking becomes impossible in conventional weft picking devices with the tapered air guide openings of air guide members intending consumed air saving, the taper of the air guide opening of each air guide member is omitted and additionally each alignment clearance, the air guide members are set at a relatively wide suitable value allowing an air stream fraction to leak therethrough. It will be appreciated from the above that an effective weft picking can be accomplished under the assistance of such air leak, upon which great air saving can be totally achieved though some air leakage is thus allowed.

Referring now to Figs. 1 to 3, there is shown a preferred embodiment of the weft picking device of an air jet loom, in accordance with the present invention. The weft picking device comprises a weft guide device 2 which is constituted by a plurality of air guide members 3. Each air guide member 3 has a generally straight section 3a and a generally curved section 3b which is branched off from the straight section. These sections 3a and 3b form a generally annular section which defines at its inner peripheral surface 3p a generally circular air guide opening 4, and additionally are formed with a slit 5 communicating with the air guide opening so that a weft yarn 12 within the air guide opening 4 is capable of passing out of the opening 4. The air guide opening 4 is formed straight without any taper.

In other words, the inner peripheral surface 3p of the above-mentioned generally annular section constituted by the sections 3a and 3b is perpendicular to a vertical plane V parallel with each air guide member 3 as shown in Fig. 3. The air guide members 3 are aligned in the direction of weft picking, and each air guide member is spaced predetermined distances from the adjacent air guide members. Each air guide member 3 is secured onto an air guide holder 6 by fixedly locating the lower portion of the straight section 3a in the groove of the air guide holder using an adhesive. The air guide openings of the successively located air guide members constitute a weft guide channel 4A through which the weft -yarn 12 injected from a main nozzle 11 travels and picked into the shed 14 of warp yarns 13.It is to be noted that the average diameter of the air guide opening 4 is set at a value smaller than the value below which weft picking is impossible in a weft picking device using air guide members having respective tapered air guide openings, i.e., set at the value smaller than 12 mm as discussed hereinbefore. Additionally, the distances of the spaces formed between the adjacent air guide members (i.e., alignment clearances of the air guide members) are set at values which prevent the weft yarn from flying out through the slit 5 under the influence of air leakage through the alignment clearances of the air guide members 3. In other words, the alignment clearances are so set as to offset or cancel the air stream fractions leaking through the air guide member slits 5 by the air stream fractions leaking through the alignment clearances.Each alignment clearance is preferably not less than 0.8 mm, and more preferably within a range from 0.8 mm to 1.6 mm, except for the clearance between the air guide members between which the auxiliary nozzle 20 is positioned. The air guide holder 6 is fixed within the groove of a reed holder 9 together with the lower frame of a reed 1. The reed holder 9 is fixedly mounted on the top section of a sley sword 8 which is fixed on a rotatable shaft 7 so as to be swingable in fore and aft directions. The shaft 7 is rotatably supported on a loom frame 7. The reference numeral 1 5 in Fig. 2 designates the cloth fel of a woven fabric 1 6. The air guide holder 6 is divided into a plurality of pieces.An auxiliary nozzle holder 1 8 is fixed using small screws on the end surface of each piece, which surface faces the loom side opposite to the main nozzle 11, except for the corresponding surface of the piece located farthest from the main nozzle.

An auxiliary nozzle 20 of the pipe shape is so supported on the holder 18 as to be located between the straight sections 3a of the adjacent air guide members 3. Accordingly, a plurality of auxiliary nozzles 20 are aligned along the weft guide channel 4A, standing parallel with air guide members 3. The inside hollow of the auxiliary nozzle 20 communicates with an air introduction pipe 21 via a passage (not shown) formed in the holder 18. The air introduction pipe 21 is fixed to the holder 18 and extends downwardly along the reed holder 9. A flexible tube 22 is connected at one end to the air introduction pipe 21, and at its other end to an air outlet of an air control valve 24 which is fixedly mounted on an elongate stay 23 extending between the opposite loom frame 17. An air inlet of the air control valve 24 is connected to a high pressure air source (not shown).

The air control valve 24 is so constructed and arranged that a valve member 25 is usually biased in the direction (downward in Fig. 2) to open the valve to supply pressurized air to the tube 22 by the action of a spring (not shown) disposed in the valve 24. The thus biased valve member 25 biases at its lower end section a swingable lever 27 whose one end is pivotally attached through alr-axial pin 26 to the body of the air control valve 24. A cam follower 28 is rotatably attached to the other end of the swingable lever 27. The cam follower 28 is arranged to contact the cam surface of a rotatable cam 30 which is fixedly mounted on a rotatable shaft 29 which rotates once per one operational cycle of the loom, i.e., per one going and returning movement of the reed 1. The cam 30 is formed with a cam lobe 30a.Accordingly, the cam follower 28 contacts the cam lobe 30a, the valve member 25 is upwardly biased through the lever 27 so as to open the valve 24 to allow pressurized air to flow to the flexible tube 22. It is to be noted that the cam 30 is so constructed that its cam lobe 30a contacts the cam follower 28 when the weft yarn 12 injected from the main nozzle 11 reaches the vicinity of the corresponding auxiliary nozzle 20.

Each auxiliary nozzle 20 is closed at its top and formed at its upper side wall with a nozzle opening 32. The top of each auxiliary nozzle 20 is formed into rounded conical shape. The nozzle opening 32 is so formed that its axis lies on a horizontal plane containing the axis G of the weft guide channel 4A and crosses the axis G at a predetermined angle 6. Accordingly, the air ejection direction line N of the auxiliary nozzle 20 angularly crosses the weft guide channel axis G and is directed to the inner surface 3a of the air guide opening 4 of the air guide member 3 which is positioned nearer the loom side opposite the main nozzle than the auxiliary nozzle 20. It is preferable that the several air guide members positioned downstream of each auxiliary nozzle 20 are formed at their air guide opening surfaces with cut-out portions 33 of rounded groove shape.This renders it unnecessary to project the auxiliary nozzle 20 into the weft guide channel 4A, thereby preventing failed weft picking due to the weft yarn 12 being caught by the auxiliary nozzle 20.

The manner of operation of the above-described weft picking device will now be discussed.

When the reed 1 moves backward, each air guide member 3 of the weft guide device 2 which moves with the reed 1 enters the warp yarn shed 14 pushing aside the warp yarns 13. Almost simultaneously, each auxiliary nozzle 20 also enters the warp yarn shed 14 pushing aside the warp yarns by the top section thereof. From the time point where the warp yarns have passed out of the weft guide channel 4A, pressurized air is ejected from the main nozzle 11 into the weft guide channel 14A, injecting the weft yarn 1 2 under the influence of the thus ejected pressurized air and the air stream formed thereby to start the weft picking.Immediately before the weft yarn leading end reaches the vicinity of each auxiliary nozzle 20, the cam lobe 30a of the cam 30 be to contact the cam follower 28, so that the valve member 25 of the air control valve 24 is pushed in through the lever 27.

Accordingly, the air control valve 24 opens to allow pressurized air to be supplied to the auxiliary nozzle 20 via the tube 22 and the pipe 21. Then an air jet is ejected from the nozzle opening 32 of each auxiliary nozzle 20 in the predetermined direction. As a result, the weft yarn 12 is carried throughout the weft guide channel 4A, being successively blown away by the air jets from the nozzle openings of the successively located auxiliary nozzles 20 to accomplish the weft picking. Each auxiliary nozzle 20 is so arranged as to stop the air jet ejection from the nozzle opening 32 thereof when weft yarn carrying action is taken over to the succeeding auxiliary nozzle 20, since the cam lobe 30a of the cam 30 separates from the cam follower 28.

When the weft picking has completed, the high pressure air ejections from the main nozzle 11 and the auxiliary nozzle 20 located farthest from the main nozzle 11 stop, and the air guide members 3 and the auxiliary nozzles 20 pass out of the warp shed 14 by the next forward movement of the reed 1.

At this time, the picked weft yarn 12 passes out of the air guide opening 4 of each air guide member 3 passing through the slit 5 under the supporting action of the lower weft yarns constituting the warp shed 14. Thereafter, the weft yarn 12 is beaten up against the cloth fel 15 by the reed 1 to weave the fabric 1 6.

Now, the state of the above-mentioned weft picking will be explained in detail with reference to Fig. 3. Fig. 3 shows the state of the weft picking under the condition which exhibited the most preferable result throughout a variety of experiments conducted under a variation of many factors of experimental conditions.The experimental conditions for Fig. 3 are follows: The inner diameter D of the air guide opening of each air guide member 3: 7 mm, the thickness T of the air guide member 3: 2.9 mm, the distance C between the air guide members 3:1.6 mm, the diameter of the nozzle opening 32 of each auxiliary nozzle 20: 1 mm, the intersecting angle 6 of the air ejection direction line N of the nozzle opening 32 relative to the axis of each air guide opening 4: 15 degrees, and the distance P between adjacent auxiliary nozzles 20: 100 mm.

As shown in Fig. 3, the weft yarn 12 was attracted toward and onto the air ejection direction line N when it approached the vicinity of the auxiliary nozzle 20. Thereafter, the weft yarn 12 crossed the axis G along the air ejection direction line N and further advanced in its advancing direction which is changed along the theoretical reflection line R to again cross the axis G. Then, the weft yarn 12 further changed its advancing direction to advance along the axis G as soon as it again crossed the axis G.

Thus the weft yarn 12 light in weight laid at a position (the center of the air stream formed in the weft guide channel) where the flow speed of the air stream is the highest, and therefore it seemed that such shape of the weft yarn indicated the center of the air stream in the weft guide channel.

In this connection, with previously proposed weft picking device (disclosed in United States Patent Application No. 149,083) wherein air guide members having tapered air guide openings are combined with auxiliary nozzles, the theoretical reflection line (indicated by the character R' in Fig. 3) of the air ejection direction line N is formed in zigzag pattern, gradually decreasing the pitches thereof.

Therefore, this exhibits the effect of effective and rapid convergence of the air stream into the axis G.

However, it will be appreciated from the shape of the reflection line R' that turbulence is generated in the air stream if the cross-sectional area of the air guide opening of each air guide member is decreased. in this regard, according to the present invention, the theoretical reflection line R having equal pitches is gently formed and therefore a stable air stream center can be formed even within a narrow weft guide channel. Additionally, the phenomena that the air stream center finally became in agreement with the axis G shows the fact that equalized air leaks take place radially through the alignment clearances of an air guide member row.

As appreciated from the above, according to the present invention, in the weft picking device of the air saving type wherein the weft yarn is picked into the weft guide channel defined by the air guide openings of a series of radially almost closed air guide members under the influence of the air jets from the main nozzle and the auxiliary nozzles, the air guide opening of each air guide member is formed straight without any taper and additionally the distance of the each alignment clearance is so set as to allow a suitable air stream fraction to leak therethrough. This permits the air guide opening of the air guide member to decrease to an extent which cannot be used in conventional weft picking devices, thereby achieving further great air saving. Although there is some air leakage in the weft picking device according to the present invention, stable weft yarn carrying action is carried out in which the weft yarn floats in the weft guide channel as shown in Fig. 3 by the assistance of the leaked air, keeping lowest the flying resistance of the weft yarn. Therefore, it is possible to decrease the number of auxiliary nozzles as compared with in the above-mentioned second conventional weft picking device and therefore the present invention greatly improves the weft picking device using the radially almost closed air guide members, from economic standpoints.

Claims

1. A weft picking device of an air jet loom, comprising: a weft inserting nozzle for injecting a weft yarn under the influences of an air jet therefrom; a plurality of air guide members aligned in the direction of weft picking, said air guide members being formed therethrough with respective air guide openings which constitute a weft guide channel through which the weft yarn from the weft inserting nozzle is picked, each air guide member being formed with a slit through which the weft yarn passes out of said air guide opening; an auxiliary nozzle disposed to eject an air jet into said weft guide channel to form an air stream in said weft guide channel;; means for forming the air guide opening of each air guide member straight, said means including an inner peripheral surface of said air guide member, said inner peripheral surface being perpendiuclar to a plane parallel with said air guide members; and means for so spacing each air guide member from adjacent air guide members as to cancel air stream fractions leaking through said air guide member slit by air stream fractions leaking through the spaces between air guide members so that the weft yarn is prevented from flying out of the weft guide channel through said air guide member slit during the weft picking.

2. A weft picking device as claimed in claim 1, wherein the average diameter of said air guide opening of each air guide member is not larger than 12 mm.

3. A weft picking device as claimed in Claim 1, wherein said spacing means includes means for setting the distance between adjacent two air guide members within a range not less than 0.8 mm.

4. A weft picking device as claimed in Claim 3, wherein said range is from 0.8 mm to 1.6 mm.

5. A weft picking device as claimed in Claim 1 , wherein said auxiliary nozzle, is positioned between two adjacent air guide members, said auxiliary nozzle being formed with a nozzle opening whose axis crosses the axis of said weft guide channel at an angle ranging from 12 degrees to 1 5 degrees.

6. A weft picking device as claimed in Claim 5, wherein the diameter of said nozzle opening is within a range from 1.0 mm to 1.2 mm.

7. A weft picking device as claimed in Claim 1 , wherein each air guide member includes a generally straight section and a generally curved section defining at their inner peripheral surfaces the straight air guide opening.

8. A weft picking device as constructed and arranged substantially as described herein with reference to, and as illustrated in, Figs. 1, 2 and 3 of the accompanying drawings.