EP1418262A1

EP1418262A1 - Weft inserting nozzle of air jet loom and pipe as used therein

Info

Publication number: EP1418262A1
Application number: EP03021475A
Authority: EP
Inventors: Hideki Banba
Original assignee: Tsudakoma Industrial Co Ltd
Current assignee: Tsudakoma Corp
Priority date: 2002-11-05
Filing date: 2003-09-23
Publication date: 2004-05-12
Also published as: JP2004156162A; CN1548596A

Abstract

A pipe (28) for use in a weft inserting nozzle of an air jet loom has a tapered portion which is formed inside the pipe (28) so as to have a shape which is gradually and continuously enlarged in the direction toward the outlet side of a fluid, thereby the flow speed of the fluid on the out let side of the fluid being made larger than that on the inlet side of the fluid, and the pipe (28) has a length of 150 mm or less. The inside of the tapered portion has a shape of which the sectional area or the diameter is gradually and continuously increased as advancing toward the outlet side of the fluid. The tapered portion has a diameter of 3 mm or more on the inlet side of the fluid and a diameter of 5 mm or less on the outlet side of the fluid. The inclination angle of the tapered portion is 0° or more but is 1° or less.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a weft inserting nozzle (main nozzle) of an air jet loom making use of the pressure air as a weft inserting fluid and also relates to a pipe for use in the weft inserting nozzle.

Prior Art

One of weft inserting nozzles is disclosed in the Japanese Patent Publication (KOUKOKU) No. 2-42930 (p. 2, Figs. 1 and 4). This prior art weft inserting nozzle includes a weft guide having a weft channel into which a weft is inserted, a main body which is arranged such that it surrounds the weft guide channel to form a fluid flowing channel, and a flow control pipe which is located to closely face to the outlet of the fluid jet and has a flow control channel for controlling a pressure fluid. The flow control channel is made up of a pipe-shaped member having a stepwise cross section, of which the area is made larger step by step as advancing toward the outlet of the fluid outlet.
The weft which is inserted into the weft channel gets into the stand-by state where the inserted weft projects out the distal end portion of it from the tip (i.e. the fluid outlet) of the flow control channel. At the time of inserting the weft, if the pressure fluid is blown into the flow control channel through the fluid flowing path, the weft is ejected out from the tip of the flow control channel and inserted into the warp-shed.
Being ejected out by a predetermined length and then beaten up with a reed, the weft is cut off at a point between the weft inserting nozzle and the woven fabric. Then, the pressure fluid is further ejected against the weft region inside the flow control channel. In other words, the pressure fluid blows the weft inserted in the flow control channel in the direction from the fluid inlet side (opposite to the fluid jet side) to the fluid outlet side (fluid jet side).
In the above prior art, when weft inserting nozzle, however, as the distal tip portion of the weft at rest inside the flow control channel is abruptly accelerated with a jet flow of the pressure fluid as soon as the weft inserting process starts, the distal tip portion of the weft existing in the weft inserting nozzle at time of starting the weft inserting process begins to violently behave inside the flow control channel, because of which the weft disadvantageously receives a damage which is apt to generate and leaves weaving defects such as a filling knot, a kink and so forth in the woven fabric.
Furthermore, as described above, the cross-sectional area of the flow control channel is made larger step by step. Because of this, if the inner diameter of one step portion is abruptly enlarged in the next step portion contiguous with the above one step portion, the flow of the pressure fluid falls into disorder in the vicinity of the boundary having abrupt step height difference between the above contiguous stepwise portions and comes to cause swirls there with ease. Due to this swirl, the flow loss of the pressure fluid becomes larger and on the contrary, the weft transporting power is reduced. The weft transporting power is a power the pressure fluid can carry the weft through the inside of the weft inserting nozzle.
Accordingly, an object of the invention is to maintain the weft transporting power as well as to prevent weaving defects from being generated in the woven fabric.
As a result of energetic researches and efforts by the inventors of this invention, it has been ascertained that the above object can be achieved by improving the length of a pipe for use in a weft inserting nozzle and the inside shape of the pipe.

SUMMARY OF THE INVENTION

According to the invention, there is provided a pipe for use in a weft inserting nozzle of an air jet loom wherein the pipe has a tapered portion which is formed inside the pipe so as to have a shape which is gradually and continuously enlarged in the direction toward the fluid outlet side, thereby the flow speed of the fluid on the fluid out let side being made larger than that on the fluid inlet side, and the pipe has a length of 150 mm or less.
If the pipe having a length of 150 mm or less is used, the most tip portion of the weft damaged due to its violent behavior in the pipe comes to be woven as a fringed selvedge portion on the opposite side of the weft feeding side. Thus, as the amount of the damaged portion remaining in the woven fabric is advantageously reduced, that is the number of weaving defects generated in the woven fabric is reduced, which necessarily results in an improvement in the quality of the woven fabric.
Besides, if the tapered portion is formed in the inside of the pipe and has a shape of which the sectional area or the diameter is continuously and gradually enlarged in the direction toward the outlet of the pressure fluid, the flow speed of the pressure fluid passing through the tapered portion is made faster. With this, there can be compensated the reduction in the weft transporting power of the weft inserting nozzle caused by shortening the length of the pipe (150 mm or less). The tapered portion having such a shape as described above is referred to as laval pipe portion in the following. Accordingly, it becomes possible to maintain the weft transporting power at a predetermined value as well as to prevent weaving defects from being generated in the woven fabric.
Now, in this specification as well as claims as per attached hereto, an expression "continuously enlarged tapered portion" does not means that the sectional area of the tapered portion is abruptly and discretely enlarged to leave a stepwise portion, but means that the sectional area of the tapered portion is smoothly enlarged without forming any stepwise portion. In other words, it means that enlargement is carried out not stepwise but non-stepwise, that is, without making use of such a plane that is in parallel with the axis of the pipe or intersects the same at a large angle, for example at right angles.
Besides, the pipe expressed as "pipe having such an inside shape that makes the flow speed of the fluid on the fluid outlet side larger than that on the fluid inlet side" may include in part a tapered portion. For instance, there may be used a pipe having a straight or non-tapered portion on the fluid inlet side or fluid outlet side as far as the pipe includes in part such a tapered portion by which the flow speed of the pressure fluid for use in the weft inserting is made continuously faster toward the fluid outlet side.
The inside of the tapered portion may have a diameter gradually and continuously increasing toward the fluid outlet side. If the pipe includes a tapered portion like the above, it becomes possible to prevent the generation of the whirlpool caused by the burble phenomenon of the pressure fluid flow, as observed in the prior art, in such a portion that the sectional area of the tapered portion is abruptly changed, like the stepwise portion.
The tapered portion may have a diameter of 3 mm or more on the fluid inlet side and a diameter of 5 mm or less on the fluid outlet side. Besides, the inclination angle of said tapered portion may be 0° or more but be 1° or less. If the tapered portion satisfies these conditions, it become possible to remove the flow loss caused by the whirlpool in the prior art, and the flow speed of the pressure fluid for the weft inserting use is surely made faster as advancing toward the fluid outlet side.
A weft inserting nozzle according to the invention includes a pipe as described in the above; a nozzle body having a penetrating hole into which the fluid inlet side of said pipe is inserted; said weft guide which is inserted into said penetrating hole from the weft inlet side and has a needle portion on said pipe side, said needle portion having the same axis as that of said tapered portion; an adjustment mechanism adjusting a gap or space between said tapered portion and said needle portion; and a nozzle portion which is formed in said penetrating hole so as to form an orifice portion around at least the tip portion of said needle portion, said orifice having an inner peripheral surface of which the diameter is made smaller as it goes toward the said pipe side.
According to the nozzle as described above, the insertion amount of the needle portion to the orifice can be adjusted by adjusting the space between the tapered portion and the needle portion by means of the adjustment mechanism as described above. Accordingly, if adjusting the above insertion amount to be small (or large), the flow quantity of the pressure fluid as flowed out from orifice is made large (or small), thereby enabling the weft transporting power to be made large (or small).

BRIEF DESCRIPTION OF THE DRAWINGS

Now, the invention will be described more in detail by way of preferred embodiments according to the invention with reference to the accompanying drawings, in which:
Fig. 1 is a diagram schematically showing the constitution of the first embodiment of a weft inserting nozzle according to the invention.
Fig. 2 is a vertical sectional view of the weft inserting nozzle as shown in Fig. 1.
Fig. 3 is an enlarged sectional view of the pipe as shown in Fig. 2.
Fig. 4 is an enlarged sectional view for explaining the laval angle of the pipe as shown in Fig. 3.
Fig. 5 is a graph showing the relation between the length of the pipe and the number of filling knots generated per a woven fabric of 1 m length.
Fig. 6 is a graph showing the relation between the length of the pipe and the weft transporting power.
Fig. 7 is an enlarged sectional view of an orifice as shown in Fig. 2.
Fig. 8 is a vertical sectional view showing the other embodiment of the pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figs. 1 through 4, a weft inserting nozzle 10 according to the invention is used as a main nozzle of the air jet loom in which the compressed air is used as a pressure fluid.
As shown in Fig. 1, the weft inserting nozzle 10 is located on the weft inserting side of a woven fabric 12. The weft 16 extending from a weft storage device 14 is inserted into the weft inserting nozzle 10 from the rear end side (left end side) of the weft inserting nozzle 10 toward the tip end side (right end side) of the same.
The weft inserting nozzle 10 has a length of L0. Because of this, in the woven fabric 12, the most part of the weft tip region corresponding to the length L0 is used as a fringed selvedge portion 18 on the counter side of the weft inserting side (right side of woven fabric in Fig. 1). Thus, only a small part of the weft tip region remains in the woven fabric 12 even if they would be left therein.
As shown in Fig. 2, the weft inserting nozzle 10 includes a cylinder-shaped nozzle body 20 having a through hole; a weft guide 22 inserted in the rear end region (left end region) of the through hole of the nozzle body 20; a fluid control device 24 arranged in the central first half region of the through hole of the cylindrical nozzle body 20; a cylinder-shaped nozzle portion 26 arranged in the central second half region of the through hole of the nozzle body 20; and a pipe 28 inserted in part in the tip end region (right end region in Fig. 2) of the through hole of the nozzle body 20.
The through hole of the nozzle body 20 penetrates the nozzle body 20 in the axial direction thereof so as to allow the weft 16 to run it through. The through hole of the nozzle body 20 coaxially contains a receiving hole 30 acting as the rear end region, the central first half region and the central second half region, and also a pipe hole 32 acting as the tip end region, into which the rear end portion (left end portion in Fig. 2) of a pipe 28 is fitted firmly.
The receiving hole 30 and the pipe hole 32 have a common axis, which is also common to all of the weft guide 22, the fluid control device 24, the nozzle portion 26 and the pipe 28. The receiving hole 30 and the pipe hole 32 have a circular shaped cross section. The diameter or the sectional area of the former is made larger than those of the latter.
The nozzle body 20 has a tapped hole 34 which is screw-coupled to a nozzle holder (not shown) supplying the pressure fluid such as the compressed air to the weft inserting nozzle 10, and a fluid introducing path 36
The weft guide 22 includes a base portion 40 coaxially inserted into the receiving hole 30 of the nozzle body 20 from the rear end side of it, an intermediate portion 42 coaxially extending from the base portion 40 toward the tip end side, a needle portion 44 coaxially extending from the intermediate portion 42 toward the tip end side, a flange portion 46 formed at the rear end of the base portion 40, and a weft guide hole 48 penetrating the weft guide 22 in the axial direction of it. The weft guide 22 also acts as a needle.
The main nozzle body 20 is fitted with the weft guide 22 by inserting the base portion 40, the intermediate portion 42 and the needle portion 44 in the receiving hole 30 such that the flange portion 46 of the weft guide 22 makes contact with the rear end surface of the main nozzle body 20 and further connecting the base portion 40 with the rear end portion of the receiving hole 30 by means of the external thread portion 50 of the base portion 40.
The base portion 40 has a circular sectional shape of which the diameter is almost the same as that of the receiving hole 30. The intermediate portion 42 has a circular sectional shape of which the diameter is shorter than that of the receiving hole 30. As a result, there is formed an annular space 52 surrounding the peripheral surface of the intermediate portion 42, which comes to form the weft guide 22 in cooperation with the main nozzle body 20. The annular space 52 communicates with the fluid introducing path 36.
The needle portion 44 is made in the shape of a thin cylinder. The peripheral surface of the needle portion 44 has a shape, of which the diameter is continuously and gradually reduced from the rear end portion of the intermediate portion 42 toward the tip end of the same, thus the peripheral surface of the needle portion 44 coming to act as an outward guide surface for guiding the pressure fluid.
The fluid control device 24 has the shape of a cylinder having an outer diameter approximately equal to the inner diameter of the receiving hole 30. Besides, the fluid control device 24 includes a plurality of control fins 54 extending in parallel with the front and rear directions, the control fins 54 of which each is arranged at least on the latter half part of the inside of the fluid control device 24 at a predetermined interval. The space between control fins 54 juxtaposed in the peripheral direction acts as a control path for controlling the flow of the pressure fluid.
The nozzle portion 26 is made in the shape of a cylinder having an outer diameter approximately equal to the inner diameter of the receiving hole 30. The diameter of the inner peripheral surface at the rear end of the nozzle portion 26 is made larger than that of the inner peripheral surface at the rear end of the pipe 28 while the diameter of the inner peripheral surface at the front end of the nozzle portion 26 is made approximately equal to that of the inner peripheral surface at the rear end of the pipe 28.
Besides, the inner peripheral surface of the nozzle portion 26 is formed in the shape of a truncated cone, in other words, the diameter of it continuously and gradually decreases toward the side of the pipe 28. As a result, the inner peripheral surface of the nozzle portion 26 comes to form an orifice 56 which squeezes and accelerates the pressure fluid passing therethrough to eject it to the inside of the pipe 28. The nozzle portion 26 may be formed to be integrated into the nozzle body 20 or the fluid control device 24.
As shown in Fig. 3, the inside of the pipe 28 has a laval shape of which the inner diameters ( a and  b) continuously and gradually increases ( a <  b) toward the ejection side of the pressure fluid (front side) like the slanting surface portion of the truncated cone.
However, the inside of the pipe 28 may include in part a linear portion at least on the tip or rear side of the slanting surface portion, the linear portion having such a diameter that neither increases continuously and gradually toward the side of ejecting the pressure fluid nor accelerates the pressure fluid, in short, a constant diameter. Besides, the cross section of the pipe 28 is not limited to be circular but it may draw a circular arc. As shown in Fig. 4, an inclination angle  continuously and gradually increasing toward the side of ejecting the fluid will be referred to as a laval angle  in the following.
In the weft inserting nozzle 10 as shown in Fig. 2, the pressure fluid like the compressed air is supplied to the fluid introducing path 36 by means of the nozzle holder (not shown). The pressure fluid supplied to the fluid introducing path 36 is supplied to the nozzle portion 26 from the annular space 52 via the fluid control device 24, and is then ejected from the nozzle portion 26 toward the inside of the pipe 28, and is further ejected from the pipe 28 toward the warp shed.
The length L of the pipe 28 as shown in Fig. 2 is set to be 150 mm or less. Because of this, even if the weft 16 thrown into the inside the pipe 28 of the weft inserting nozzle 10 takes a violent behavior and is damaged therein, the most tip region of that weft 16 is used in the fringed selvedge portion 18 on the right side of the woven fabric 12 as shown in Fig. 1. Thus, even a small part of the damaged weft is prevented from being woven into the woven fabric under the weaving operation. As a result, generation of weaving defects in the woven fabric 12 can be effectively suppressed and the quality of the woven fabric 12 can be improved very much.
The pressure fluid supplied to the weft inserting nozzle 10 is controlled by the fluid control device 24 such that it is squeezed and accelerated by the nozzle portion 26. On one hand, as the length L of the pipe 28 is short like 150 mm or less as mentioned above, there is reduced as usual the power of the weft inserting nozzle 10, that is, the power for transporting the weft.
However, in case of the weft inserting nozzle 10 according to the invention, as the tapered portion inside the pipe 28 has a shape of which the sectional area or the diameter continuously and gradually increases toward the ejection side of the pressure fluid and also the flow speed of the pressure fluid passing through the pipe 28 is made faster toward the ejection side of the pressure fluid, the reduction in the weft transporting power of the weft inserting nozzle 10 due to the short length (150 mm or less) of the pipe 28 is compensated by accelerating the flow speed of the pressure fluid through the tapered portion of the pipe 28. Accordingly, with the weft inserting nozzle 10 like this, it becomes possible to maintain the weft transporting power at a predetermined level as well as to prevent weaving defects from being generated in the woven fabric.
The inventors of this invention have performed the following tests with regard to the weft inserting nozzle 10 as described above and have found the optimum values with respect to the weft inserting nozzle 10, especially to the shape of the pipe 28. The weaving condition is set in common for every test as follows: the width of the woven fabric is 1675 mm and the revolution speed of the loom is 700 rpm.

[Test 1: Comparison between Pipes of Straight/Laval Type]

In Test 1, there are prepared three kinds of weft inserting nozzles for test (referred to as test piece hereinafter) 1, 2 and 6 including one each of various pipes 28 having dimensions different from one another as shown in the following Table 1. These test pieces are incorporated in sequence into a predetermined loom one by one and then, the test weaving of a fabric is carried out by mean of that loom.
Table 1 indicates the number of filling knots (weaving defects in the woven fabric) included in the woven fabric of 1m length as well as the measured value of the pressure value (referred to as "MP" hereinafter) of the weft inserting nozzle (only main nozzle). The value of the MP indicates the pressure that is needed for obtaining the same predetermined flying speed of the weft. Accordingly, the smaller the value of the MP is, the larger the weft transporting power becomes.
It will be recognized from Table 1 that in case of the test piece 2 of the laval type, the MP of it indicates the lowest value (i.e. the highest weft transporting power) comparing with MP's of test pieces 1 and 6. On one hand, with regard to the number of the filling knots, the test piece 2 indicates a maximum value comparing with the test pieces 1 and 6. Besides, it will be recognized from Table 1 that in case of the test piece 1 of the straight type, the number of the filling knots becomes zero but the MP of it indicates the highest value (i.e. the lowest weft transporting power).

[Test 2: Comparison on Length of Laval Type Pipe]

In Test 2, there are again prepared three other test pieces 3, 4 and 5 which are formed by shortening the pipe length L of test piece 2 of the laval type indicating the best MP value in Test 1. To put it more concretely, the standard pipe length of 220 mm of the test piece 2 is shortened to 160 mm for test piece 3, to 135 mm for test piece 4 and to 110 mm for test piece 5 as shown in Table 1, respectively. Similar to Test 1, one each of these test pieces is incorporated into a predetermined loom, and the test weaving of a fabric is carried out by mean of this loom, during which the number of filling knots and the value of the MP are measured.
The results of the above Test 2 are shown also in Table 1. Referring to the test results with regard to the test piece 2 as used in Test 1 as well as the test result with regard to the test pieces 3 through 5 as used in Test 2, it is recognized that if the length L of the pipe is made shorter, the weft transporting power is decreased. Contrary to this, it is recognized that if the length L of the pipe is made longer, the weft transporting power is increased.
Accordingly, the mutual relation among the pipe shape of the weft inserting nozzle, the number of filling knots and the weft transporting power can be shown in the form of Table 2 based on the results of Tests 1 and 2. Furthermore, a relation between the number of filling knots and the pipe length L, and the relation between the weft transporting power and the pipe length L can be drawn in the form of graphs as shown in Figs. 5 and 6.
It is recognized from Fig. 5 that the longer the length L of the pipe is made, the more filling knots are generated. In other words, it is recognized that the number of filling knots as generated can be sharply decreased by shortening the length L of the pipe. The allowable number of filling knots is judged according to an empirical rule, for instance the number of filling knots in a woven fabric of 1m length be within a few filling knots or less. Accordingly, as recognized from the graph shown in Fig. 5, the upper limit of the pipe length L is preferably set to be 150 mm or less.
From the graphs as shown in Fig. 6, it is recognized that if the pipe length L is set to be 150 mm or less, the weft transporting power or the MP value is substantially not dropped. This is apparent from the data shown in Table 1. That is, despite that the MP value of the laval type test piece 5 is lower than the MP value of the test piece 6, the weft transporting power is not dropped so much.
The following things are recognized from Table 2 and Figs. 5 and 6. That is, it is recognized that the use of the laval type pipe increases the weft transporting power, but on the other hand, it also increases generation of the filling knot. In case of using the straight type pipe, the weft transporting power reaches its top level defined and limited by the pipe configuration. Even if it is tried to extend the pipe length L and/ or to enlarge the inner diameter of the pipe in order to break through such limitation by the pipe configuration, to increase the weft transporting power is not free but has to be restricted at a certain level due to the choke phenomenon. Accordingly, it is possible to specify such a laval shape that hardly generates filling knots based on the suitable design of laval angle  and the length L of the pipe.
If taking account of the easy insertion of the weft into the reed groove as well as application to a multiple color loom (two or more colors), it is preferable to set the inner diameter  b of the end portion on the fluid outlet side (weft outlet side) of the pipe to be smaller, such as  5 mm or less, more preferably  4 mm to  5 mm. Besides, it is preferable to set the inner diameter  a of the end portion on the fluid inlet side (weft inlet side) of the laval type pipe to be  3 mm or more, more preferably  3 mm to  4 mm by taking account of the relation with the above inner diameter  b on the fluid outlet side of the pipe.

[Test 3: Comparison on Laval Angle ]

In Test 3, three other test pieces 7, 8 and 9 as shown in Table 1 are prepared based on the test data obtained in Test 1 and Test 2 as well. Similar to these Tests 1 and 2, each of these test pieces is put in the test weaving of a fabric to obtain the number of filling knots in the woven fabric and the MP value.
In the above test piece 7, the length of the pipe is made equal to that (110 mm) of the pipe in the test piece 5 which shows the least number of filling knots in Test 2 and the laval angle  is changed from 0.38° to 0.29° .
The pipe of the above test piece 8 is a laval type pipe which is formed by enlarging the inner diameter on the outlet side of the pipe in the test piece 1 from  3 mm to  3.5 mm.
The pipe of the above test piece 9 is formed by shortening the length of the pipe in the test piece 6 from 220 mm to 110 mm.
The results of Test 3 are also shown in Table 1, from which it is recognized that the test piece 7 generates the least number of filling knots. This results from three factors, that is, the first is that the length of the pipe is shortened; the second is that a laval angle  is suitable, and the third is that the MP value is lower.
Besides, an additional test is carried out with regard to the test piece 7 under such a condition that the revolution speed of the main shaft of the loom is increased up to be 850 rpm. As a result additional test, it is indicated that six filling knots are generated and the MP value becomes 0.437 MPa. Accordingly, it is recognized that if the revolution speed of the main shaft of the loom is set to be at a comparatively higher level, the number of the filling knots as generated is still within the acceptable level.
As will be apparent from the various test results as described above, it becomes possible to achieve the object of the invention, that is, to maintain the weft transporting power as well as to prevent weaving defects from being generated in the woven fabric by providing a weft inserting nozzle including a pipe, which has a length of 150 mm or less, a tapered portion of which the inner diameter is continuously and gradually increased toward the outlet side of the pressure fluid, the inner diameter of the tapered portion on the inlet side from which the weft is introduced is  3 mm or more while the inner diameter of the tapered portion on the outlet side of the weft is  5 mm or less, and the inclination angle  of the tapered portion is 0° or more but 1° or less. However, if the inclination angle  of the tapered portion exceeds 1° , it would be hardly possible to get a good result because of the burble phenomenon in the pressure fluid.
Referring to Fig. 7, in the above weft inserting nozzle 10, the positional relation between the nozzle portion 26 and the tip end portion of the needle portion 44 can be changed by adjusting the amount (length) of the screw-engaged portion between the base portion 40 of the weft guide 22 and the nozzle body 20. Therefore, the screw-engaged portion between the base portion 40 and the nozzle body 20 acts as an adjustment mechanism for adjusting a gap or space between the tapered portion and the needle portion 44.
Accordingly, the insertion amount of the needle portion 44 into the orifice 56 can be adjusted by adjusting the space between the tapered portion and the needle portion by means of the adjustment mechanism as described above. Thus, if adjusting the above insertion amount to become smaller (or larger), the flow quantity of the pressure fluid as flowed out from orifice 56 is made larger (or smaller), thereby the weft transporting power being made larger (or smaller). Besides, it is possible to change the flow amount of the pressure fluid flowing out from orifice 56 as well as the weft transporting power by replacing the weft guide 22 with that which is able to shorten (or elongate) the above insertion length into the orifice 56.
Furthermore, as shown in Fig. 8, the inside of the pipe 28 has a shape of which the inner diameter ( a and  b) continuously and gradually increases ( a <  b) toward the outlet of the pressure fluid. In this case, the increase rate of the inner diameter may change so as to draw a slanting curve which continuously and gradually increases according to an exponential function.
The nozzle portion 26 may be integrated into the nozzle body 20 or the fluid control device 24.
While some embodiments of the invention have been shown and described in the above with reference to the accompanying drawings, the invention is not limited to those embodiments. Various changes and modifications will be possible without departing from the gist of the invention.

Claims

A pipe (28) for use in a weft inserting nozzle of an air jet loom wherein said pipe (28) has a tapered portion which is formed inside said pipe so as to have a shape which is gradually and continuously enlarged in the direction toward the fluid outlet side, thereby the flow speed of said fluid on said fluid outlet being made larger than that on the fluid inlet side, and said pipe has a length of 150 mm or less.
A pipe (28) for use in a weft inserting nozzle as claimed in claim 1, wherein the inside of said tapered portion has a shape of which the sectional area or the diameter is gradually and continuously increased as advancing toward said fluid outlet side.
A pipe (28) for use in a weft inserting nozzle as claimed in claim 1 or 2, wherein said tapered portion has a diameter of 3 mm or more on the fluid inlet side and a diameter of 5 mm or less on said fluid outlet side.
A pipe (28) for use in a weft inserting nozzle as claimed in any one of claims 1 through 3, wherein the inclination angle of said tapered portion is 0° or more but is 1° or less.
A weft inserting nozzle comprising:

a pipe (28) for use in a weft inserting nozzle as claimed in any one of claims 1 through 4;

a nozzle body (20) having a penetrating hole (30,32) into which the fluid inlet side of said pipe (28) is inserted;

a weft guide (22) which is inserted into said penetrating hole (30,32) from the weft inlet side and has a needle portion (44) on said pipe (28) side, said needle portion (44) having the same axis as that of said tapered portion;

an adjustment mechanism (50) for adjusting a gap or space between said tapered portion and said needle portion (44), and

a nozzle portion (26) which is formed in said penetrating hole (30,32) so as to form an orifice portion around at least the tip portion of said needle portion (44), said nozzle portion (26) having an inner peripheral surface of which the diameter is made smaller as advancing toward the said pipe (28) side.