Weft yarn grasping apparatus for fluid jet loom

The weft yarn is selectively gripped and released by movable and stationary disc members in response to the weaving operation of the loom. The gripping force applied to the weft yarn by the members is such controlled that under beating of the reed, the magnitude of the force is decreased by a predetermined value thereby inducing a slippage of the weft yarn in the members.

BACKGROUND OF THE INVENTION 
The present invention relates in general to a fluid jet weaving loom, such 
as water jet loom and/or air jet loom, and more particularly to a weft 
yarn grasping apparatus functioning to selectively grasp and release the 
weft yarn which is picked into the shed of the warp yarns by the aid of 
fluid jet stream in response to the weaving operation of the loom. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved weft yarn 
grasping apparatus for a fluid jet weaving loom, the apparatus 
contributing substantially to production of fabric of good quality. 
It is another object of the present invention to provide an improved weft 
yarn grasping apparatus the gripping force of which is such controlled 
that under beating up of the reed, the magnitude of the gripping force is 
decreased by a predetermined value thereby inducting a slippage of the 
weft yarn by the apparatus, so that the undesirable weft yarn breakage 
which has been caused by an application of an abnormally big tension to 
the weft yarn under beating is eliminated. 
It is still another object of the present invention to provide an improved 
weft yarn grasping apparatus the operation of which does not cause an 
abnormally big tension to the weft yarn under beating is eliminated. 
It is a further object of the invention to provide an improved weft yarn 
grasping apparatus which is produced by slightly modifying the 
conventional weft yarn grasping apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Prior to explaining the construction of the grasping apparatus of the 
subject invention, a description of the conventional grasping apparatus 
will be given with the aid of FIGS. 1 and 2 in order to clarify the 
inventive steps of the invention. 
Referring to FIG. 1 of the drawing, there is schematically illustrated a 
conventional fluid jet weaving loom which is generally designated by 
numeral 10. The loom 10 comprises a weft yarn measuring device 12 by which 
a predetermined length of weft yarn 14 is withdrawn from a weft yarn 
supplier (not shown). A weft yarn storage tube 16 is arranged to receive 
therein the predetermined length of the weft yarn 14 by the aid of air 
stream flowing in the illustrated direction P. Denoted by numeral 18 is a 
weft yarn grasping apparatus which functions to selectively grasp and 
release the weft yarn 14 coming from the storage tube 16. A fluid jet 
nozzle 20, such as air jet nozzle and water jet nozzle, receives therein 
the weft yarn 14 from the grasping apparatus 18 for throwing the same into 
a shed (no numeral) of longitudinally parallelly arranged warp yarns 22, 
the shed being formed by heddles 24a and 24b. A reed 26 is perpendicularly 
arranged on the warp yarns 22 to beat up the weft yarn 14 just thrown into 
the shed for the nozzle 20 thereby to form a fabric 28. Designated by 
numerals 30 are heat cutters which cut end sections of the penetrated weft 
yarn 14 after the beating of the reed 26. 
In FIG. 2, a detailed construction of the conventional weft yarn grasping 
apparatus 18 is shown in a sectional manner. The apparatus 18 generally 
comprises a gripping device 18a and an actuating device 18b. 
The gripping device 18a comprises a cylindrical base member 32 which has at 
its lower section an extension 34 threaded via a connecting nut 35 in an 
opening (no numeral) formed in a frame member 36 of the loom 10 and at its 
upper section an exteriorly threaded portion (no numeral). Screwed and 
fixed to the threaded portion is a holding ring 38 which has a central 
opening 40 through which a stationary disc member 42 is tightly attached 
on an upper portion of the base member 32. The stationary disc member 42 
and the base member 32 are respectively formed with a central opening 44 
and a central passage 46 which are vertically aligned to each other to 
slidably receive therein a reciprocating rod 48. The rod 48 is equipped at 
its upper end, projected from the stationary disc member 42, with a 
cup-shaped disc member 50 via connecting nuts 52 screwed to a threaded 
extension 48a of the rod 48. Hereinafter, the cup-shaped disc member 50 
will be referred as a movable disc member for facilitation of the 
description. The movable disc member 50 has a flat lower surface portion 
(no numeral) which faces to a flat upper surface portion (no numeral) of 
the stationary disc member 42. Between the flat surface portions of the 
movable and stationary disc members 50 and 42 is inserted the weft yarn 14 
which is fed from the weft yarn storage tube 16 (FIG. 1). As shown, the 
rod 48 is equipped at its lower end section, projected from the base 
member extension 34, with a retainer 54 for disposing a compression spring 
56 between it and the extension 34 to urge the reciprocating rod 48 
downwardly, that is in a direction to move the movable disc member 50 
toward the stationary disc member 42 thus grasping the weft yarn 14. 
For intermittently pushing up the rod 48 and thus the movable disc member 
50 to release the weft yarn 14, the actuating device 18b is employed, 
which comprises a first lever 58 pivotally supported at its fulcrum 60. 
The first lever 58 has a left end 58a contactable with a convex surface 
formed on the downwardly extending end of the reciprocating rod 48. A 
spring 62 is disposed between the left side of the lever 58 and the frame 
member 36 to urge the lever in a counterclockwise direction. The first 
lever 58 has a right end 58b which is contactable with a lower end of an 
adjusting screw 64 fixed to a second lever 66. The second lever 66 is 
pivotally supported at its fulcrum 68 and has a left end 66a to which the 
adjusting screw 64 is fixed and a right end 66b to which a cam follower 70 
is rotatably fixed. A tension spring 72 is fixed to the right side of the 
second lever 66 for biasing the same to rotate in a clockwise direction 
forcing the cam follower 70 to operatively engage with a cam 74 which is 
tightly disposed about an axis 76. The axis 76 is arranged to rotate one 
time per one pcking action of the loom 10, in a counterclockwise direction 
as indicated by an arrow A. The cam 74 has thereon a projected cam surface 
74a and a non-projected cam surface 74b, as shown. 
With this, in operation, when the cam follower 70 rises on the projected 
cam surface 74a of the cam 74, as hereinillustrated, the second lever 66 
takes a position to allow the first lever 58 to push upwardly the 
reciprocating rod 48 and thus the movable disc member 50 to release the 
weft yarn 14 from the gripping device 18a, while when the cam follower 70 
slides on the non-projected cam surface 74b of the cam 74, the second 
lever 66 takes the other position to allow the first lever 58 to swing in 
a counterclockwise direction by the action of the springs 56 and 62 
allowing the reciprocating rod 48 and thus the movable disc member 50 to 
move toward or return to its home position by the action of the spring 56 
to grip the weft yarn 14. 
However, in the fluid jet loom equipped with the above-mentioned type weft 
yarn grasping apparatus 18, there arises such a severe problem that a 
remarkably high tension is inevitably applied to the weft yarn 14 under 
beating up of the reed 26 thereby causing snapping of the weft yarn and 
occurrence of crucks in the weft yarn 14. This is because when the reed 26 
is carried from its rest position to the beating position, the weft yarn 
14 having been just inserted into the shed of the warp yarns 22 is forced 
to stretch by a certain length "l" as is shown in FIG. 1. In fact, this 
type grasping apparatus 18 is constructed to tightly grip the weft yarn 14 
without permitting a bit of the same to slip out therefrom while the reed 
26 operates to beat up the weft yarn 14. 
Japanese Patent Provisional Publication referenced by TOKKOSHO No. 47-51986 
discloses a weft yarn grasping apparatus which can partially solve the 
above-mentioned drawback. The grasping apparatus of this Publication is 
constructed to completely release the weft yarn under the beating of the 
reed. However, in this disclosed apparatus, there arises further problem 
in which the weft yarns penetrated into the warp yarns in every picking 
actions are remarkably changed in length and the tension given to each 
weft yarn becomes too low to make a good fabric. 
Thus, as described hereinbefore, the present invention contemplates the 
elimination of the above-stated several drawbacks encountered in the 
conventional weft yarn grasping apparatus. 
Reference is now made to FIG. 3, there is illustrated an improved weft yarn 
grasping apparatus of the first preferred embodiment according to the 
invention, the apparatus being generally designated by numeral 78. The 
grasping apparatus 78 of this embodiment generally comprises a weft yarn 
gripping device 78a and an actuating device 78b which are somewhat similar 
in construction to the devices 18a and 18b of the above-mentioned 
conventional apparatus 18 of FIG. 2. Thus, substantially same or similar 
parts are designated by the same numerals as in the case of FIG. 2. 
The gripping device 78a includes a reciprocating rod 49 having at its upper 
end 49c a small diameter extension 49a the length of which is sufficiently 
greater than that of the extension 48a of the conventional gripping device 
18a mentioned above. The extension 49a slidably passes through an opening 
(no numeral) formed in a base section 80a of a cup-shaped disc member 80 
and then connects at its top end to a stop member 82 via a connecting nut 
74. The cup-shaped disc member 80, similar to the before-mentioned movable 
disc member 50 of FIG. 2, has a flat lower surface or flange portion 80b 
which faces to the flat upper surface portion of the stationary disc 
member 42. It should be noted that the cup-shaped disc member 80 is 
permitted to slide along the extension 49a between the stop member 82 and 
the upper end 49c of the rod 49 from which the extension 49a protrudes. 
Thus, hereinafter, the cup-shaped disc member 80 will be referred as a 
movable disc member. A compression spring 86 is concentrically disposed 
around the movable disc member 80 between the stop member 82 and the 
flange portion 80b of the movable disc member 80 so that the movavle disc 
member 80 is biased downwardly that is in a direction toward the 
stationary disc member 42. Now, it is also to be noted that the biasing 
force produced by the spring 86 is set sufficiently smaller than that of 
the spring 56' disposed between the retainer 54 fixed to the rod 49 and 
the lower extension 34 of the base member 32. Thus, when the reciprocating 
rod 49 is not given as upwardly biasing force by the first lever 58, the 
rod 49 locates at its lower most position with a result that the stop 
member 82 tightly abuts on the base section 80a of the movable disc member 
80 strongly urging the same toward the stationary disc member 42. Under 
this state, the weft yarn 14 is tightly or strongly gripped by the 
gripping device 78a. While, when the rod 49 is lifted upwardly a slight 
distance by the first lever 58, the stop member 82 is separated from the 
movable disc member 80 while keeping the same at its previously set 
position with the aid of the spring 86, as will be understood from FIG. 5. 
Under this state, the gripping force applied to the weft yarn 14 by the 
gripping device 78a is somewhat reduced to such a value that the 
sandwiched weft yarn 14 is caused to slipperily slide in the gripping 
device 78a when it is pulled by a predetermined magnitude of force in its 
travelling direction. Furthermore, when the rod 49 is lifted up more by 
the first lever 58 the upper end 49c of the rod proper 49 is brought into 
contact with the inner surface of the base section 80a of the movable disc 
member 80 and finally, the movable disc member 80 is lifted to a position 
to define a large clearance between the movable disc member 80 and the 
stationary disc member 42, as will be well understood from FIG. 4. Under 
this state, the weft yarn 14 is completely released from the gripping 
device 78a. 
As shown in FIG. 3, the actuating device 78b of the first preferred 
embodiment comprises generally same parts as in the conventional one 18b 
of FIG. 2 except for a cam 75 fixed to the axis 76. The cam 75 is formed 
to have first and second projected cam surfaces 75a and 75c and first and 
second non-projected cam surfaces 75b and 75d, the projected cam surfaces 
and the non-projected cam surfaces being arranged alternatively as shown. 
It should be noted that the height of the first projected cam surface 75a 
is sufficiently greater than that of the second projected one 75c and is 
substantially same as the projected cam surface 74a of the 
before-mentioned conventional cam 74 of FIG. 2. 
With this construction of the grasping apparatus 78, the operation of it is 
as follows: 
For facilitation, the explanation of the operation will be given with the 
aid of FIG. 1. When picking or insertion of the weft yarn 14 into the shed 
of the warp yarns 22 is taken, the cam 75 takes a position in which the 
first projected cam surface 75a engages the cam follower 70 as seen in 
FIG. 4. The engagement of the cam surface 75a with the follower 70 induces 
a state in which the first lever pushes up the reciprocating rod 49 to its 
uppermost position with a result that the movable disc member 80 is lifted 
up to completely release the weft yarn 14 from the gripping device 78a. 
Thus, the weft yarn picking is surely achieved. 
After the weft yarn insertion, the cam 75 is rotated to take a position 
wherein the non-projected cam surface 75b engages the cam follower 70 as 
seen in FIG. 3. During this, the first lever 58 swings in a 
counterclockwise direction by action of the springs 56 and 62 in response 
to the clockwise swing of the second lever 66. Thus, the rod 49 moves 
downwardly by the action of the spring 56' to its lowermost position 
causing the gripping device 78a to tightly or strongly grip the weft yarn 
14. 
When the beating of the reed 26 is taken, the cam 75 takes a position in 
which the second projected cam surface 75c engages the cam follower 70, as 
seen in FIG. 5. Under this, the second lever 66 and thus the first lever 
58 are moved to slightly lift up the reciprocating rod 49 thus separating 
the stop member 82 from the movable disc member 80. Thus, as has been 
described hereinbefore, the gripping force applied to the sandwiched weft 
yarn 14 is somewhat reduced. Now, the gripping force to the weft yarn 14 
is made by only the spring 86. Accordingly, if the penetrated weft yarn 14 
is subjected to a tension application which is greater than a 
predetermined value by the beating of the reed 26, the gripping device 78a 
permits the slippage of the weft yarn 14 therein thereby substantially 
cancelling the abnormal tension in the weft yarn 14. Now, it should be 
noted that such slippage occurs only when the magnitude of the tension 
exceeds the predetermined value. 
After the beating of the reed 26, the cam 75 takes a position wherein the 
other non-projected section 75d engages the cam follower 70 causing the 
gripping device 78a to tightly grip the weft yarn 14. 
FIG. 6 shows graphically in terms of the cyclic displacement of the reed 26 
from one beat up position to the next, the zone in which picking of the 
weft yarn 14 into the shed of warp yarns 22 is possible and the gripping 
force applied to the weft yarn 14 by the gripping device 78a. 
Referring to FIG. 7, there is shown a fragmentary view of a modified form 
of the gripping device 78a according to the first embodiment. In this 
modification, a pair of permanent magnets 88a and 88b are employed as a 
substitute for the spring 86 of the gripping device 78a. These magnets 88a 
and 88b are respectively fixed to the stop member 82 and the base section 
80a of the movable disc member 80 in such a manner that same poles thereof 
face each other to produce effective repulsive force between them. With 
this, the repulsion force produced by the magnets 88a and 88b is applied 
to the movable disc member 80 during the movements of it so that 
substantially same function as in the case of the gripping device 78a with 
the spring 86 is achieved in this modified case. 
Referring to FIG. 8, there is illustrated a second preferred embodiment of 
the subject invention, as being generally designated by numeral 90. The 
grasping apparatus 90 of this embodiment generally comprises first and 
second gripping devices 92a and 94a and first and second actuating devices 
92a and 94b, the first and second actuating devices 92b and 94b being 
respectively incorporated with the first and second gripping devices 92a 
and 94a, as shown. 
The first and second gripping device 92a and 94a are arranged in tandem 
with respect to the passage of the weft yarn 14. Preferably, the first 
gripping device 92a is located upstream of the second gripping device 94a. 
Each of the devices 92a and 94a comprises generally same parts as in the 
case of the conventional gripping device 18a. Thus, similar or 
substantially same parts are denoted by the same numerals as in the case 
of the conventional gripping device 18a. In this embodiment, however, the 
biasing force of the spring 86' of the second gripping device 94a is set 
sufficiently smaller than that of the spring 56' of the first gripping 
device 92a. More specifically, the springs 56' and 86' are formed to have 
substantially the same characteristics as the springs 56 and 86 of the 
first preferred embodiment shown in FIG. 3, so that the gripping force 
produced by the first gripping device 92a is considerably greater than 
that of the second gripping device 94a. For accommodation with the 
actuating devices 92b and 94b which will be described hereinnext, first 
and second cam followers 96 and 98 are rotatably fixed to lower ends of 
the reciprocating rods 100 and 102. 
The first and second actuating devices 92b and 94b respectively have a 
first cam 104 firmly disposed about a first axis 106 and a second cam 108 
firmly disposed about a second axis 110. These axes 106 and 110 are 
arranged to rotate once per one picking action, in the directions 
indicated by arrows A. The cam 104 of the first actuating device 92b is 
formed with first and second projected cam surface 104a and 104c which are 
same in height, and first and second non-projected cam surfaces 104b and 
104d. The second cam 108 of the second actuating device 94b is formed with 
a projected cam surface 108a and a non-projected cam surface 108b. It 
should be noted, in this instance, that the first projected cam surface 
104a of the first cam 104 and the projected cam surface 108a of the second 
cam 108 have substantially same effective length thereby to have same 
operation timing with respect to the weaving operation of the loom. 
With the above, the operation of the grasping apparatus 90 of the second 
embodiment is as follows: 
When the weft yarn picking is taken, the first projected cam surface 104a 
of the first cam 104 and the projected cam surface 108a of the second cam 
108 engage their corresponding cam followers 96 and 98. Under this state, 
the corresponding reciprocating rods 100 and 102 and thus the movable disc 
members 50 and 50 are lifted to completely release the weft yarn 14. Thus, 
the weft yarn picking is smoothly achieved. 
After the weft yarn insertion or picking, the first non-porjected cam 
surface 104b of the first cam 104 and the non-projected cam surface 108b 
of the second cam 108 engage the corresponding cam followers 96 and 98 
thereby allowing the rods 100 and 102 to shift into their lowermost or 
home positions by the action of the springs 56' and 86'. Under this, the 
weft yarn 14 is gripped by the first and second gripping devices 92a and 
94a. In this instance, the weft yarn gripping force applied by the second 
gripping device 94a is not so great in comparison with that of the first 
gripping device 92a because of using the relatively weak spring 86' as has 
been described hereinbefore. 
Upon beating of the reed 26, the second projected cam surface 104c of the 
first cam 104 engages the first cam follower 96 while the non-projected 
cam surface 108b of the second cam 108 still engages the second cam 
follower 98. Under this, the movable disc member 50 of the first gripping 
device 92a is lifted to release the weft yarn 14, while the movable disc 
member 50 of the second gripping device 94a keeps its weft yarn gripping 
position. Thus, if the weft yarn 14 is abnormally pulled toward the shed 
of the warp yarns 22 due to the beating operation of the reed 26, a slight 
slippage of the weft yarn 14 is carried out in the second gripping device 
94a thereby cancelling the tension of the weft yarn 14. As has been 
described hereinbefore, such slippage occurs only when magnitude of the 
tension exceeds the predetermined value. 
After the beating of the reed 26, the second non-projected cam surface 104d 
of the first cam 104 engages the first cam follower 96 thus causing the 
first gripping device 92a to tightly grip the weft yarn 14. 
In FIG. 9, a third preferred embodiment of the subject invention is shown 
as being designated by numeral 112. The grasping apparatus 112 of this 
third embodiment generally comprises a gripping device 112a and an 
actuating device 112b which are somewhat similar to the before-mentioned 
second gripping device 94a and the second actuating device 94b of the 
grasping apparatus 90 according to the second embodiment, except for 
several parts. Thus, similar or substantially same parts are denoted by 
the same numerals as in the case of the second embodiment 90. The gripping 
device 112a of the third embodiment is equipped with a bias controlling 
device 114 which functions to control the biasing force of the spring 86', 
the spring 86' being used for biasing the reciprocating rod 102 and thus 
the movable disc member 50 toward the cam 108. The bias controlling device 
114 includes a lever 116 having an end pivotted by a fulcrum 118 and the 
other end which is enlarged to have an opening 120 through which the lower 
section of the reciprocating rod 102 is slidably passed. As shown, the 
other end of the lever 116 engages or holds the upper end of the spring 
86' so that swingable movements of the lever 116 induce changing of the 
biasing force of the spring 86'. A cam follower 122 is rotatably fixed to 
the lever 116 at a position near the pivotted end thereof. A cam 124 
having a projected cam surface 124a and a non-projected cam surface 124b 
is firmly disposed about an axis 126 so as to operatively engage the cam 
follower 122. Similar to the axis 110 for the cam 108, the axis 126 rotate 
one time per one picking action of the loom. It will be thus appreciated 
that when the projected cam surface 124a engages the cam follower 122, the 
lever 116 takes a position, shown by a solid line, to strongly push the 
spring 86' to generate a big force in the same, and when the non-projected 
cam surface 124b engages the cam follower 122, the lever 116 takes a 
position, shown by a phantom line, to softly push the spring 86' to 
generate a small force in the same. The cam 124 is such arranged that the 
engagement of the non-projected cam surface 124b with the cam follower 122 
is made when the picking action takes place. Thus, under the weft yarn 
picking, the grasping force produced by the spring 86' is somewhat reduced 
even when the reciprocating rod 102 is placed in its lower most position 
due to the engagement of the non-projected cam surface 108b of the cam 108 
with the cam follower 98, so that the weft yarn slippage occurs.