Method for injecting transport fluid into a shed from auxiliary jet nozzles

A method for injecting a transport fluid into a shed from a plurality of auxiliary jet nozzles is disclosed. In general, the auxiliary jet nozzles successively discharge the jets of fluid in time with advancement of a weft thread through the shed to thereby assist the weft in being transported with a jet of fluid launched by a main jet nozzle. According to the invention, the periods of time of discharge of the auxiliary jet nozzles are prolonged with the advancement of the weft through the shed.

BACKGROUND OF THE INVENTION 
This invention relates to a jet loom, and more particularly to a method for 
injecting a transport fluid into a shed from auxiliary jet nozzles of the 
jet loom, wherein a weft thread is inserted into the shed by using the 
jets of injected fluid under pressure. 
Generally, in a jet loom of such type, a main jet nozzle alone can not 
transport the leading end of the weft to a distance at a sufficient speed, 
so that a suitable number of auxiliary jet nozzles are provided on a reed 
to each produce a flow of air in cooperation with the main jet nozzle. 
However, if all the auxiliary jet nozzles are always operated, a great 
total consumption of air results. In order to reduce the total 
consumption, U.S. Pat. No. 3,705,608 has proposed to energize the 
auxiliary jet nozzles successively or in successive groups in time with 
the advancement of the leading end of the weft thread through the shed. 
Because each auxiliary jet nozzle is operated for the same period of time 
as the others, the injection timing of the auxiliary jet nozzles has to be 
adjusted when a transport speed of the weft is varied due to changes in 
thickness, kind of material and degree of fluffiness of the weft, and due 
to changes in operation speed of the loom. More specifically, in order to 
allow the weft to be effectively subjected to the function of the jets 
from the auxiliary jet nozzles, it is required that the injection timing 
of the auxiliary jet nozzles be advanced when the weft is transported at a 
higher speed and delayed when the same is transported at a lower speed. 
Furthermore, even if weaving conditions are maintained unchanged, both the 
transport speed and the path of the weft will be subject to fluctuations 
each time a weft insertion operation is carried out, and the fluctuations 
will be gradually increased toward the end of one weft inserting 
operation. This causes the injection timing of the auxiliary jet nozzles 
to become out of time with the advancement of the weft leading end, thus 
resulting in the weft not being inserted. 
It is therefore a principal object of this invention to provide a method 
for injecting a transport fluid into a shed from auxiliary jet nozzles, 
which requires no adjustment of the injection timing of the auxiliary jet 
nozzles even when weaving conditions are changed. 
SUMMARY OF THE INVENTION 
With the above object in view, this invention resides in a method for 
injecting a transport fluid into a shed from a plurality of auxiliary jet 
nozzles, which successively discharge jets of fluid in time with the 
advancement of a weft thread through the shed, to thereby assist the weft 
in being transported with a jet of fluid launched by a main jet nozzle, 
characterized in that the periods of time of discharge of the auxiliary 
jet nozzles are prolonged with the advancement of the weft through the 
shed.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, particularly to FIGS. 1 and 2, there is 
shown a reed 1 having a plurality of equi-spaced guide plates 1a 
perpendicularly mounted on a reed frame 2. Disposed adjacent the endmost 
guide plate 1a is a main jet nozzle 3, which may be connected to a supply 
of pressurized air (not shown) and discharges a jet of air under high 
pressure to transport a weft thread, which has been threaded into the main 
jet nozzle 3, through a shed defined by upper and lower warp sheets Y and 
the reed 1. The reed frame 2 also has mounted perpendicularly thereon a 
plurality of equi-spaced auxiliary jet nozzles N, each of the auxiliary 
jet nozzles N being constructed and arranged in a conventional manner so 
that the upper end portion thereof is positioned adjacent a guide path 1b 
formed by the guide plates 1a, thereby allowing the jet of air under 
pressure discharged therefrom in the direction, in which the weft is to be 
transported, to assist the weft in being transported through the guide 
path 1b. 
Although a jet loom is generally provided with ten or more auxiliary jet 
nozzles, the method according to this invention will be described, only by 
way of example, with reference to an embodiment employing eight auxiliary 
jet nozzles N1 to N8. 
In the diagram of FIG. 3, a time to perform a weft inserting operation is 
drafted on the abscissa X, and a width of auxiliary jet nozzle arrangement 
is shown on the ordinate Z. Assuming that the weft thread travels at 
normal constant speed, its leading end will be transported along the 
straight line OT, wherein a point O is a point in time at which 
transportation of the weft by the first auxiliary jet nozzle N1 starts, 
and a point T is a point in time at which the leading end of the weft has 
just passed through the shed. However, it is to be noted that 
transportation of the weft to the first auxiliary jet nozzle N1 has been 
carried out by the jet from the main jet nozzle 3, and that the air 
injection from the first auxiliary jet nozzle N1 commences simultaneously 
with the main jet nozzle 3. 
At the beginning of the weft inserting operation, the main jet nozzle 3 
injects the weft together with the jet of high pressure air to transport 
the weft into the shed, and at the same time, in addition to the first and 
second jet nozzles N1 and N2, the auxiliary jet nozzles N3 to N8 are 
operated for a predetermined short period of time t to discharge the jets 
simultaneously, whereby the flow of air is established along the overall 
length of the weft path in the shed. 
Then, the third to eighth auxiliary jet nozzles N3 to N8 are made 
inoperative to discontinue the simultaneous discharges therefrom, while 
the first auxiliary jet nozzle N1 further discharges the jet of for a 
period of time t1 (&gt;t) to assist the weft in being transported near the 
first auxiliary jet nozzle N1. With respect to the second auxiliary jet 
nozzle N2, it further continues to discharge the jet of air for a 
predetermined period of time t2 (&gt;t1)even after it is passed by the weft. 
Before the weft leading end reaches a position adjacent the third auxiliary 
jet nozzle N3 and immediately after the jet nozzles N3.about.N8 are 
rendered inoperative, the third jet nozzle N3 is again operated for a 
predetermined period of time t3+t4 (t4&gt;t2), wherein at the end of t3 the 
weft leading end passes beside the third jet nozzle N3. 
The weft leading end then reaches a position adjacent the fourth jet nozzle 
N4. However, the fourth jet nozzle N4 is again operated for a period of 
time t5 (t5&gt;t3) in advance prior to arrival of the weft leading end to the 
fourth jet nozzle N4 and continues to discharge the jet for a period of 
time t6 (&gt;t4) after the arrival of the same. 
The fifth to eighth jet nozzles N5 to N8 also can be operated in the same 
manner as the third and fourth jet nozzles N3 and N4. That is, they are 
made operative successively in phase overlapped relationship so that each 
succeeding auxiliary jet nozzle is operative for a longer period of time 
than the adjacent preceding auxiliary jet nozzle to thereby assist the 
weft leading end in being transported beside the jet nozzles N5 to N8. In 
addition, it is seen from FIG. 3 that a period of time, during which the 
compressed air is discharged from the last jet nozzle N8, is prolonged in 
order to provide a certain tension in the weft until it is beaten up. 
Where the transport speed of the weft is decreased due to changes in 
thickness, kind of material, degree of fluffiness of the weft and changes 
in operation speed of the loom, the time necessary to complete one weft 
insertion operation will be prolonged as shown by the line OA in FIG. 3. 
Even then, all the jets injected from the auxiliary jet nozzles N1 to N8 
will be able to serve to effectively transport the weft leading end 
through the shed. In contrast to the above, where the transport speed of 
the weft is increased due to changes in weaving conditions of the loom, 
the time to perform one weft insertion operation will be shortened as 
understood from the line OB shown in FIG. 3. Under this condition, all the 
jets injected from the auxiliary jet nozzles N1 to N8 also will be able to 
serve to effectively transport the weft leading end through the shed. 
Thus, in any case, there is no need to adjust the injection timing of the 
auxiliary jet nozzles N1 to N8. 
Actually, during one weft inserting operation, the speed of the weft 
leading end varies as the leading end advances through the shed. 
Therefore, although the leading end actually follows a line P, all the 
jets injected from the auxiliary jet nozzles N1 to N8 serve to effectively 
transport the weft leading end in the same manner. Thus, there is no need 
to adjust the injection timing of the auxiliary jet nozzles N1 to N8. 
In addition, even when the leading end of the weft advances at constant 
speed as shown by the lines OA, OT and OB, a widthwise position of the 
leading end in the shed at any point of time during the weft inserting 
operation changes with the transport speed of the weft. And, an amount of 
change gradually increases as the weft leading end advances toward the end 
of the shed remote from the main jet nozzle. The method according to the 
invention can accommodate such a change in widthwise position of the weft, 
since a period of injection time for each succeeding auxiliary jet nozzle 
is more prolonged than the preceding auxiliary jet nozzles. 
In the illustrated embodiment, all the auxiliary jet nozzles N1 to N8 are 
adapted to be simultaneously operated at the beginning of the weft 
inserting operation, thus providing a flow of pressure air along the 
overall length of the weft path in the shed. This causes the weft thread 
launched by the main jet nozzle to be transported smoothly through the 
shed. In this respect, it is to be noted that, where the auxiliary jet 
nozzles N1.about.N8 are operated successively during the normal weft 
inserting operation without the simultaneous air supply from all the jet 
nozzles N1.about.N8 at the beginning of the weft inserting operation, 
vortexes will occur locally in the flow of compressed air from each 
auxiliary jet nozzle, which vortexes prevent a smooth weft insertion 
operation. However, in the illustrated embodiment, the flow of air is 
first established along the overall length of the shed to provide a 
minimum amount of turbulence, thus resulting in most favourable weft 
inserting conditions. 
Especially, even when the loom is in one picking motion or operated at a 
low speed (at that time the auxiliary jet nozzles operated in synchronism 
with the weaving motion of the loom are delayed in injection timing 
relative to the advancement of the leading end of the weft) such, for 
example, as during the preparatory operation immediately after looming, 
when it is necessary to re-insert a new weft after the weft breakage, when 
it is necessary to observe an inserting condition of the new weft before 
the normal operation re-starts, when it is necessary to confirm the 
position of the cloth fell upon occurrence of trouble, and when it is 
necessary to observe a condition by giving one picking motion to the loom, 
the weft insertion operation can be accomplished without error because the 
flow of air is established along the overall length of the weft path in 
the shed. 
However, the above-described step of simultaneously injecting the jets from 
all of the auxiliary jet nozzles may be performed at any point of time in 
the course of the weft inserting operation and may be eliminated because 
it is not essential to the invention. 
It is therefore apparent that the present invention has provided a method 
for injecting a transport fluid into a shed from auxiliary jet nozzles, 
which requires no adjustment of the injection timing of the auxiliary jet 
nozzles even when weaving conditions are changed.