Standby weft yarn cutting preventing device for a multicolor fluid jet loom

A standby weft yarn cutting preventing device is provided for a multicolor fluid jet loom, such as a multicolor air jet loom. In cutting a picked weft yarn among a plurality of weft yarns with the cutter of the loom, the standby weft yarn cutting preventing device drives away the free ends of the rest of the weft yarns from the operating zone of the cutter to prevent the free ends of the weft yarns on standby from being cut together with the picked weft yarn.

BACKGROUND OF THE INVENTION 
1. Field of the Invention: 
The present invention relates to a multicolor fluid jet loom which in 
operation carries out a cutting blow, and more particularly, to a device 
for preventing the cutting of a weft yarn which need not be cut on such a 
multicolor fluid jet loom. 
2. Description of the Prior Art: 
In a multicolor fluid jet loom, a plurality of weft yarns are picked 
sequentially in a predetermined order, and the picked weft yarn is cut 
with a cutter provided on the picking side of the multicolor fluid jet 
loom. While the picked weft yarn is cut with the cutter, the free ends of 
the rest of the weft yarns, namely, the standby weft yarns, are extending 
outside of their corresponding picking nozzles. In case the free end of 
the standby weft yarn nears the picked weft yarn, the cutter erroneously 
cuts the free end of the stanby weft yarn. As a result, the free end of 
the thus cut standby weft yarn is blown towards a shed of a warp yarn by a 
cutting blow and inserted into a fabric. 
The term "cutting blow" refers to a cutting blow system provided with 
multicolor fluid jet looms. The cutting blow is a small amount of fluid 
which is continuously jetted from a picking nozzle during the period of 
operation of the jet loom other than a picking period. Alternatively, a 
small amount of fluid may be jetted from the picking nozzle just before 
an/or just after a cutting operation. These small jets of fluid ensure 
that a picked weft yarn is extended and prevented from slipping off of or 
being extracted from its picking nozzle after the picked weft yarn has 
been cut by the cutter. Faulty cutting occurs frequently when hard yarns, 
such as hard twist yarns or glass yarns, are used as weft yarns. When such 
stiff yarns are used as weft yarns, the fluid is jetted continuously at a 
moderate rate from the picking nozzles to prevent the standby weft yarns 
from slipping off from the picking nozzles. The free end of the hard twist 
yarn is untwisted and extended by the jet of fluid to enter the operating 
zone of the cutter. When the glass yarn is used as a weft yarn, a portion 
of the picked glass yarn is slackened between the weft yarn storage device 
and the cutter used to cut the glass yarn, because the glass yarn is 
stiff. Then, a slack free end of a standby glass yarn is extended by the 
fluid being continously jetted from the picking nozzle and thereby the 
free end of the standby glass yarn reaches the cutting position of the 
cutter entailing erroneous weft yarn cutting. Accordingly, the multicolor 
fluid jet loom must be equipped with a standby weft yarn cutting 
prevention device. 
Japanese Utility Model Publication No. 51-5570 discloses a weft yarn 
withdrawing device, which withdraws the free end of the standby weft yarn 
with a lever from the picked weft yarn to avoid the entanglement of the 
free end of the standby weft yarn with the picked weft yarn. This known 
weft yarn withdrawing device is capable of surely preventing erroneous 
weft yarn cutting. Nevertheless, the weft yarn withdrawing device is a 
complicated mechanism and inevitably applies an excessive tension to the 
weft yarn in withdrawing the weft yarn by hooking the weft yarn with the 
lever, often damaging the weft yarn. Thus, the weft yarn withdrawing 
device is not an effective solution of the problem from the viewpoint of 
maintaining the quality of the fabric. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a standby 
weft yarn cutting preventing device for a multicolor fluid jet loom, 
capable of avoiding the erroneous cutting of the free end of a standby 
weft yarn in cutting a picked weft yarn. 
To achieve the object of the invention, the present invention provides a 
standby weft yarn cutting prevention device having an air current 
generating device which blows air in an air current in a direction other 
than the picking direction to positively separate the free end of the 
standby weft yarn from the picked weft yarn so that the free end of the 
standby weft yarn will not approach the operating zone of the cutter when 
the cutter cuts the picked weft yarn. The air current generating device is 
provided commonly for a plurality of picking nozzles or individually for 
each of a plurality of picking nozzles to apply an air current only to the 
standby weft yarn when the cutter cuts the picked weft yarn. 
Thus, according to the present invention, erroneous cutting of the weft 
yarn can surely be avoided by a simple air current generating device 
preventing the detrimental insertion of the erroneously cut piece of the 
weft yarn into the fabric. Since the device of the present invention does 
not employ any mechanical restraining device, the standby weft yarn or 
yarns will never be damaged, and hence does not cause any defects in the 
fabric and does not deteriorate the quality thereof. 
When the loom is provided with a control valve capable of controlling an 
air supply for a cutting blow, the standby weft yarn cutting preventing 
device of the present invention can be completed by simply providing the 
loom with the air current generating device. Therefore, the standby weft 
yarn cutting preventing device of the present invention can readily be 
incorporated into an existing loom as well as into a new loom. 
The above and other objects, features and advantages of the present 
invention will become more apparent from the following description taken 
in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is described herein below with reference to two 
preferred embodiments of a multicolor fluid jet loom employing a cutting 
blow system, wherein a small amount of fluid, i.e. a weak air current, is 
jetted from a picking nozzle during the period of time other than a 
picking period. 
First Embodiment (FIG. 1) 
FIG. 1 shows a standby weft yarn cutting preventing device 2 of the present 
invention incorporated into a multicolor fluid jet loom 1. In this case, 
the multicolor fluid jet loom 1 is a two-color fluid jet loom. 
The multicolor fluid jet loom 1 is provided with two picking nozzles 31 and 
32 held by a nozzle holder 4. The picking nozzles 31 and 32 are operated 
selectively in a predetermined sequence to jet a fluid, for example, air, 
so that two kinds of weft yarns 51 and 52 are picked selectively in a 
predetermined sequence into the shed 7 of warp yarn 6. The picked weft 
yarns 51 and 52 are cut by a cutter 8 disposed between the picking nozzles 
31 and 32 and the selvage of the fabric on the picking side. The picking 
nozzles 31 and 32 are connected respectively through control valves 101 
and 102 by pipes 91 and 92 to a tank 11, which in turn is connected to a 
compressed air source 12. 
The standby weft yarn cutting preventing device 2 has a single air current 
generating unit 13 is common for both the picking nozzles 31 and 32, and a 
plurality of control valves, in this embodiment two control valves 141 and 
142. The air current generating unit 13 is connected to one end of a pipe 
153. The other end of the pipe 153 is branched into two branches, which 
are connected respectively to the control valves 141 and 142. The control 
valves 141 and 142 are connected respectively through pressure regulating 
valves 161 and 162 by pipes 151 and 152 to the tank 11. The air current 
generating unit 13 blows compressed air in an air current in a direction 
other than the picking direction, for example, in a direction across the 
picking direction. In this embodiment, the respective outlet ports of the 
control valves 141 and 142 are connected also respectively to the 
respective inlet ports of the picking nozzles for a cutting blow, which is 
described in Japanese Patent Publication No. 59-44419. The control valves 
141, 142 may be electromagnetic On-Off valves for controlling 
simultaneously the cutting blow fluid and cutting prevention fluid and 
controlled by the output from a weft yarn selecting unit 17. Since the 
selection order of the weft yarns is predetermined, the weft yarn 
selecting unit 17 releases the control valve 101 or 102 at the picking 
time on the basis of the selection order, while the weft yarn selecting 
unit 17 opens simultaneously the control valve 141 or 142 at the time of 
cutting of weft yarns 51, 52 by the cutter 8. Alternatively, control 
valves 141 and 142 may be mechanical On-Off valves. When mechanical on-off 
valves are employed as the control valves 141 and 142, the control valves 
141 and 142 are operated by cams or the like in synchronism with the 
weaving operation of the loom. When electromagnetic on-off valves are 
employed as the control valves 141 and 142, the control valves 141 and 142 
are operated by electric signals provided by the weft yarn selecting unit 
17. The pressure regulating valves 161 and 162 regulate the pressure of 
air supplied to the air current generating unit 13 and air supplied to the 
picking nozzles 31 and 32 for the cutting blow below the pressure of air 
supplied to the picking nozzles 31 and 32 for picking. Regulating valves 
161, 162 may be manually preset prior to operation to regulate the air 
pressure. 
The multicolor fluid jet loom 1 opens the control valves 101 and 102 
selectively one at a time according to a predetermined picking order to 
pick the weft yarns 51 and 52 selectively into the shed 7 of the warp 
yarns 6 respectively with the picking nozzles 31 and 32. The picked weft 
yarns 51 and 52 are cut by the cutter 8 disposed between the picking 
nozzles 31 and 32 and the selvage on the picking side. 
During the operation of the cutter 8, the control valves 141 and 142 are 
opened selectively to operate the air current generating unit 13. 
When the picking nozzle 31 is operated to pick the weft yarn 51 and the 
picked weft yarn 51 is cut by the cutter 8 as shown in FIG. 1, the control 
valve 141 is opened to supply compressed air to the air current generating 
unit 13 to blow the free end of the weft yarn 52 away from the operating 
zone of the cutter 8 by the air current generating unit 13, and to the 
picking nozzle 31 for the cutting blow to urge the picked weft yarn 51 in 
the picking direction by a small force so that the cutter 8 never cuts the 
free end of the weft yarn 52. Since the picked weft yarn 51 is held by the 
warp yarns and the picking nozzle 31 prior to the cutting operation of the 
cutter 8, the picked weft yarn 51 will not be blown outside the operating 
zone of the cutter 8 by a weak air current blown by the air current 
generating unit 13, and hence the cutter 8 never fails to cut the picked 
weft yarn 51. Accordingly, the cutter 8 cuts only the picked weft yarn 51. 
Since the control valve 141 is controlled so that the weft yarn 51 is 
exposed to an air current blown at a moderate pressure through the picking 
nozzle 31 also after the same has been cut, the free end of the weft yarn 
51 is not pulled back and hence will not slip off the picking nozzle 31. 
Second Embodiment (FIG. 2) 
FIG. 2 shows a standby weft yarn cutting preventing device 2 of a second 
embodiment according to the present invention, incorporated into a 
two-color fluid jet loom 1. The standby weft yarn cutting preventing 
device in the second embodiment is substantially the same in constitution 
as the standby weft yarn cutting preventing device in the first 
embodiment, except that the former is provided with two air current 
generating units 131 and 132 individually for the picking nozzles 31 and 
32, and the control valves 141 and 142 are associated respectively with 
the air current generating units 131 and 132. The air current generating 
units 131 and 132 are actuated selectively so as to blow air only while 
the associated weft yarns 51 and 52 are on standby. A guide plate 16 
provided between the respective extremities of the picking nozzles 31 and 
32 prevents the interference of the picked weft yarn with air currents 
blown by the air current generating units 131 and 132 to further ensure 
the function of the air current generating units 131 and 132. According to 
the present embodiment the control valves 101, 102, 141, 142 may be 
controlled by the weft yarn selecting unit 17 as in the previous 
embodiment. However, the control valves 101, 102, 141, 142 may also be of 
the mechanically operated type, wherein the valves would be independently 
rotatably driven by a known cam mechanism in response to the picking 
order. Note that according to the present embodiment, the control valves 
141, 142 act respectively for controlling the cutting blow of the picking 
nozzles 31, 32, but the mechanism for providing the cutting blow could be 
alternatively provided independently of the control valves 141, 142. 
The air current generating units 13, 131 an 132 may be air blowers or 
negative pressure generating units which generate a negative pressure by 
the agency of jet of compressed air on the principle of a vaporizer. 
Although the invention has been described in its preferred form with a 
certain degree of particularity, it is to be understood that many 
variations and changes are possible in the invention without departing 
from the scope thereof.