Weft yarn sensor

A reflector is provided which produces from an incident light projected from one of two portions confronting each other at the gap of the sensor body to the other portion a reflected light offset with respect to the incident light in a direction lateral to the longitudinal direction of the weft yarn passed through the gap.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a weft yarn sensor for a weaving 
loom which senses the proper picking or insertion of the weft yarn into a 
predetermined position during the operation of the weaving loom and 
particularly to a weft yarn sensor for use in a fluid jet shuttleless 
weaving loom in which a weft yarn is inserted via a jet flow of fluid such 
as air which entrains the weft yarn and is guided or passed into the 
predetermined position through apertures formed in guiding members of an 
air guiding comb for preventing the diffusion of the fluid flow and a 
reduction in or a loss of the impetus of the fluid flow. 
2. Description of the Prior Art 
As is well known in the art, a conventional weft yarn sensor of this type 
includes a sensor body 10 as shown in FIG. 1 of the accompanying drawings 
which is located on a side of the air guiding comb near the weft yarn 
catching means and is swingably supported together with the air guiding 
comb and the reed. The sensor body 10 has two arms 11 and 12 defining an 
aperture 13 therebetween and formed so as to define a gap 14 between the 
ends thereof. The weft yarn 15 is passed through the apertures of the 
guiding members, and subsequently passed through the aperture 13 of the 
sensor body 10, then passed through gaps formed in the guiding members and 
the gap 14 of the sensor body 10 outside the apertures of the guiding 
members and the aperture 13 in the midst of the movement of the reed into 
its beat-up position. The arm 11 is provided with light projecting means 
16 formed of light conductive means e.g. optical fibers which transmits 
light from a light source to the end of the arm 11 and projects the light 
to the end of the arm 12. The arm 12 is provided with light receiving 
means 17 such as, for example, photoelectric cell which receives the light 
projected from the light projecting means 16 to the end of the arm 12. The 
light projecting and receiving means 16 and 17 both are in the form of a 
circle at the ends of the arms 11 and 12. 
When the weft yarn 15 is passed through the gap 14 outside the aperture 13, 
it intercepts the light projected from the light conductive means 16 to 
vary the quantity of light received by the light receiving means 17. This 
causes a change in the output of a light receiving device such as 
phototransistor connected to the photoelectric cell to sense that the weft 
yarn 15 has been properly inserted into the predetermined position. 
However, in the conventional weft yarn sensor, since only one beam is 
intercepted by the weft yarn 15 passed through the gap 14, a change in the 
quantity of light intercepted by the weft yarn 15 is extremely small and 
the time when the weft yarn 15 intercepts the beam is several milliseconds 
and accordingly fairly short. Thus, a change in the output of the light 
receiving device can not be sufficiently sensed by a sensing circuit and 
accordingly the conventional weft yarn sensor has been unable to surely 
and easily sense whether a weft yarn has been satisfactorily inserted into 
the predetermined position or not during loom operation. 
Furthermore, when a fly fluff is sticked to the light projecting and/or 
receiving means 16 and/or 17 at the ends of the arms 11 and 12, since the 
fly fluff is in the form of a ball or a disk, it intercepts the light 
projected to the light receiving means 17 so that the conventional weft 
yarn sensor has malfunctioned as if the weft yarn has been properly 
inserted even through the weft yarn has in fact not been properly 
inserted. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the invention to provide an improved weft 
yarn sensor in which a weft yarn passed through the gap of the sensor body 
intercepts successively at least two beams with a time lag and overlap for 
greatly increasing the time during which the weft yarn intercepts light 
incident on light receiving means so that a change in the output of a 
light receiving device is surely and easily sensed. 
It is a further object of the invention to provide an improved weft yarn 
sensor which can surely sense whether a weft yarn has been properly 
inserted or not without being influenced by attaching of a fly fluff to 
light projecting and/or receiving means. 
These object are accomplished by providing reflector means which produces 
from a beam projected from the light projecting means a reflected beam 
incident on the light receiving means, and by making the form of each of 
the ends of the light projecting and receiving means elongate in the 
longitudinal direction of the weft yarn passed through the gaps.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
Referring to FIG. 2 of the drawings, there is shown a part of a weft yarn 
sensor according to the invention. The weft yarn sensor, generally 
designated by the reference numeral 20, comprises a sensor body 22 having 
a form about similar to that of each of the guiding members of the guiding 
comb as mentioned hereinbefore. The sensor body 22 comprises a trunk 
portion 24, an upright arm portion 26 extending from the trunk portion 24 
and having a free end portion 28, and a crescent arm portion 30 laterally 
branching off from the trunk portion 24. The crescent portion 30 is curved 
toward the free end 28 of the upright portion 26 so that an aperture 32 is 
formed between the upright and crescent portions 26 and 30. The crescent 
portion 30 has a free end portion 34 confronting and spaced from the free 
end 28 of the upright portion 26 a suitable distance so that a clearance 
36 is formed between the free ends 28 and 34. The aperture 32 forms part 
of a weft yarn guiding passage through which a weft yarn 38 is passed when 
it is inserted into a shed of warp yarns (not shown). The gap 36 provides 
communication between the aperture 32 and the outside thereof so that the 
inserted weft yarn 38 is allowed to pass from the aperture 32 to the 
outside thereof. The illustration of a lower portion of the trunk portion 
24 is omitted for purpose of brevity. The lower portion of the trunk 
portion 24 is fixedly supported in a support beam (not shown) together 
with the guiding members of the guiding comb and the reed so that the reed 
is angularly moved into and away from its beat-up position together with 
the guiding comb and the sensor body 22. 
The weft yarn sensor 20 also comprises first light transmitting or 
conductive means 40 extending from the trunk portion 24 to the free end 34 
of the crescent portion 30, a second light transmitting or conductive 
means 42 extending from the free end 34 of the crescent portion 30 to the 
trunk portion 24 and spaced from the first light conductive means 42, and 
a reflector 44 securely received in the free end 28 of the upright portion 
26 and confronting the light conductive means 40 and 42. Each of the light 
conductive means 40 and 42 comprises a light conductive fiber such as, for 
example, optical fiber. The light conductive means 40 forms a light 
projecting or emitting portion which transmits light from a light source 
(not shown) such as, for example, light emission diode to an upper end 45 
of the light conductive means 40 and projects the light from the end 45 to 
the reflector 44. The reflector 44 is formed and oriented in such a manner 
as to reflect the incident light 46, projected from the light conductive 
means 40, to an upper end 47 of the light conductive means 42. The light 
conductive means 42 forms a light receiving portion which transmits the 
reflected light 48 from the upper end 47 to a light receiving device (not 
shown) such as, for example, phototransistor. It is necessary to arrange 
the light conductive means 40 and 42 out of alignment with each other at 
the end portion 34 in the longitudinal direction of the weft yarn 38 
passed through the gap 36 or to arrange the light conductive means 42 at 
the end 34 offset from a line which passes through the light conductive 
means 40 and which is parallel with the center line (not shown) of the 
aperture 32 so that the reflected and incident lights 46 and 48 are 
successively intercepted by the weft yarn with a time lag and overlap. The 
light conductive means 40 and 42 are received respectively in bores or 
grooves formed in the sensor body 22. The light projecting and receiving 
means 40 and 42 each extend into the lower portion of the trunk portion 24 
and are connected with or associated with the light source and the light 
receiving device, respectively, which both are fixedly received in the 
support beam. The light receiving device is connected to a sensing circuit 
(not shown) to feed thereto an output signal representative of the 
quantity of light transmitted by the light receiving means 42. 
When the inserted weft yarn 38 is passed through the aperture 32 and then 
passed through the gap 36 outside the aperture 32 in the midst of movement 
of the sensor body 22 together with the reed and the guiding comb (both 
not shown) into beat-up position, it intercepts two beams, that is, the 
incident and reflected beams 46 and 48 to reduce the light quantities 
incident on the reflector 44 and the light conductive means 42 as shown 
respectively in FIGS. 3(a) and (b) of the drawings. As shown in FIGS. 3(a) 
and (b), since a lag is existent between the times when the weft yarn 38 
intercepts the incident and reflected beams 46 and 48, respectively, the 
time when the weft yarn reduces 38 the quantity of light transmitted to 
the light receiving device by the light conductive means 42 is greatly 
increased as shown in FIG. 3(c) of the drawings as compared with the time 
when a weft yarn reduces the quantity of light transmitted to a light 
receiving device in the case of the conventional weft yarn sensor shown in 
FIG. 1 in which the weft yarn intercepts only one beam such as either of 
the incident and reflected beams as shown in either of FIGS. 3(a) and (b). 
In this manner, since the time when the light fed to the light receiving 
device is intercepted by the weft yarn is fairly long as compared with the 
case of the conventional weft yarn sensor of FIG. 1, variations in the 
quantity of light transmitted to the light receiving device can be surely 
sensed by the sensing circuit. 
Although the weft yarn sensor 20 has been described such that the light 
conductive means 40 and 42 are received in the trunk and crescent portions 
24 and 30 and the reflector 44 is located in the free end 28 of the 
upright portion 26, the weft yarn sensor 20 may be modified such that the 
light conductive means 40 and 42 are received in the trunk and upright 
portions 24 and 26 and the reflector 44 is located in the free end 34 of 
the crescent portion 30. The light conductive means 40 and 42 may be 
fixedly mounted on an exterior surface of the sensor body 22 in lieu of 
receiving the means 40 and 42 in the sensor body 22. 
Referring to FIG. 4 of the drawings, there is shown a part of a weft yarn 
sensor characterized in that the number of beams intercepted by the weft 
yarn 38 is increased to three (3). In FIG. 4, like component elements are 
designated by the same reference numerals as those used in FIG. 2. The 
weft yarn sensor, generally designated by the reference numeral 50, 
comprises the first light conductive means 40, the reflector 44, a 
reflector 52 fixedly secured to the free end 34 of the crescent portion 30 
and confronting the reflector 44, and second light conductive means 54 
extending from the free end 28 of the upright portion 26 to the trunk 
portion 24 and confronting the reflector 52. The second light conductive 
means 54 is received in a bore or groove formed in the sensor body 22 and 
is connected to or associated with the light receiving device as mentioned 
hereinbefore. The reflector 44 reflects therefrom to the reflector 52 the 
incident light projected from the first light conductive means 40. The 
reflector 52 reflects therefrom to the second light conductive means 54 
the incident light reflected from the reflector 44. 
It is necessary to arrange the light conductive means 40 and a point of the 
reflector 52 which receives the reflected light from the reflector 44 out 
of alignment with each other at the end portion 34 in the longitudinal 
direction of the weft yarn 38 passed through the gap 36 outside the 
aperture 32 or to arrange the reflector 52 at the end portion 34 offset 
from a line which passes through the light conductive means 40 and which 
is parallel with the center line of the aperture 32 so that the reflected 
light and the incident light are successively intercepted by the weft yarn 
with a time lag and overlap. It is also necessary that the light 
conductive means 54 is located at the end portion 28 offset from a line 
which passes through the reflector 44 and which is parallel with the 
center line of the aperture 32 so that the weft yarn 38 intercepts 
successively the reflected light from the reflectors 52 and 44 
respectively with a time lag. 
In the weft yarn sensor 50 thus constructed and arranged, when the weft 
yarn 38 is passed through the gap 36 outside the aperture 32 prior to 
beat-up operation of the reed, it intercepts successively three beams, 
that is, the beam incident on the reflector 44, and the beams reflected 
respectively from the reflectors 44 and 52. Accordingly, since the weft 
yarn 38 intercepts the light transmitted from the light conductive means 
40 to the light conductive means 54, for a time longer than the time when 
the weft yarn 38 intercepts the light transmitted from the means 40 to the 
means 42 in the case of the weft yarn sensor 20 shown in FIG. 2, the 
sensing circuit can more surely sense variations in the quantity of light 
transmitted to the light receiving device and variations in the output of 
the light receiving device as compared with the case of the weft yarn 
sensor 20 of FIG. 2. 
Although the weft yarn sensor 50 has been described such that the light 
projected from the first light conductive means 40 is increased to two 
reflected beams by the provision of the two reflectors 44 and 52, the 
light projected from the means 40 can be increased to three or more 
reflected beams by the provision of three or more reflectors. 
Referring to FIGS. 5 and 6 of the drawings, there is shown a part of a weft 
yarn sensor characterized in that it is constructed and arranged in such a 
manner that the weft yarn 38 passed through the gap 36 intercepts a 
reflected light focussed by a reflector. In FIGS. 5 and 6, like component 
elements are designated by the same reference numerals as those used in 
FIG. 2. The weft yarn sensor, generally designated by the reference 
numeral 56, comprises the first and second light conductive means 40 and 
42, and a reflector 58 fixedly received in the free end 28 of the upright 
portion 26 and confronting the light conductive means 40 and 42. The 
reflector 58 comprises a concave mirror having a segmental spherical 
internal surface or a segmental cylindrical internal surface in this 
embodiment. The reflector 58 reflects the light, projected from the light 
conductive means 40, to the light conductive means 42 and is formed and 
arranged in such a manner that the reflected light is focussed at a 
predetermined position in the gap 36 as shown at the point 59 in FIG. 5 
which position lies in a plane in which the weft yarn 38 is passed through 
the gap 36. The light conductive means 40 and the reflector 58 are 
constructed and arranged relative to each other in such a manner that the 
incident and reflected lights are offset with respect to each other in a 
direction perpendicular to the longitudinal direction of the weft yarn 38 
passed through the gap 36. 
In the weft yarn sensor 56 thus described, when the weft yarn 38 is passed 
through the gap 36 outside the aperture 32 and intercepts the light 
reflected by the reflector 58 and focussed at the predetermined position 
prior to intercepting of the incident light projected from the light 
conductive means 40 to the reflector 58, since the weft yarn 38 increases 
a variation in the quantity of light transmitted to the light receiving 
device and causes a variation in the output of the light receiving device 
as compared with the case in which a reflected light not focussed is 
intercepted by a weft yarn passed through a gap of a sensor body as in the 
weft yarn sensor 20 of FIG. 2 and the conventional weft yarn sensor of 
FIG. 1, the variation in the output of the light receiving device can be 
more surely sensed by the sensing circuit. 
Referring to FIGS. 7 and 8 of the drawings, there is shown a part of a weft 
yarn sensor characterized in that each of the incident and reflected 
lights has a form which is fairly elongate in the longitudinal direction 
of the weft yarn 38 passed through the gap 36 or inserted through the 
aperture 32. In FIGS. 7 and 8, like component elements are designated by 
the same reference numerals as those used in FIG. 2. The weft yarn sensor, 
generally designated by the reference numeral 60, comprises the first and 
second light conductive means 40 and 42, and the reflector 44, similarly 
to the weft yarn sensor 20 of FIG. 2. In this embodiment, each of the 
light conductive means 40 and 42 comprises a plurality of light conductive 
elements which, for example, comprises a plurality of light conductive 
fibers. The light conductive fibers are arranged in alignment with each 
other at the free end 34 of the crescent portion 30 in the longitudinal 
direction of the weft yarn 38 passed through the gap 36 by suitable 
fastening means, as shown in FIG. 8. The fastening means comprises two 
thin boards or members 62 and 64 of rectangle forms fixedly secured to the 
free end 34 of the crescent portion 30 in this embodiment and the two rows 
of the light conductive fibers 40 and 42 are interposed between the thin 
boards 62 and 64 as shown in FIG. 8. The reflector 44 reflects the 
incident light, projected from the light conductive fibers 40, to the 
light conductive fibers 42. 
In the weft yarn sensor 60 thus described, when the weft yarn 38 passed 
through the gap 36 outside the aperture 32 intercepts the reflected light 
from the reflector 44 and the incident light from the light conductive 
fibers 40, the quantity of light intercepted by the weft yarn 38 is fairly 
increased as compared with the case in which, for example, the weft yarn 
intercepts light projected from the end of the first light conductive 
means which end has the form of a circle as the conventional weft yarn 
sensor of FIG. 1. Accordingly, since, when the weft yarn 38 intercepts the 
reflected and incident lights from and to the reflector 44, respectively, 
a change in the quantity of light transmitted to the light receiving 
device is fairly increased as compared with the conventional weft yarn 
sensor, a change in the output of the light receiving device can be surely 
sensed by the sensing circuit. Also, since each of the light conductive 
means 40 and 42 has a form elongate in the longitudinal direction of the 
inserted weft yarn, the whole face of each of the light conductive means 
40 and 42 is prevented from being covered by a fly fluff which is usually 
in the form of a ball or a disk. As a result, whether a weft yarn has been 
properly inserted into a predetermined position or not is surely sensed 
without being influenced by attaching of the fly fluff to the light 
conductive means 40 and/or 42. 
When each of the light conductive fibers 40 and 42 has a diameter which is 
about equal to or smaller than that of the weft yarn 38, since a change or 
a decrease in the quantity of light transmitted to the light receiving 
device when the light is intercepted by the weft yarn 38 is further 
increased, a change in the output of the light receiving device can be 
more surely sensed by the sensing circuit. Also, similar result is 
obtained by making the distance between the thin boards 62 and 64 or the 
diameter of each of the light conductive fibers 40 and 42 about equal to 
or smaller than the radius of the weft yarn 38. 
Each of the light conductive means 40 and 54 can be formed of a plurality 
of light conductive members such as a plurality of optical fibers which 
have respectively ends located at the corresponding end portion 28 or 34 
and are arranged at the ends in alignment with each other in the 
longitudinal direction of the weft yarn 38. It is desirable that each of 
the optical fibers has a diameter which is not larger than that of the 
weft yarn 38. 
Although the weft yarn sensor 60 has been described such that each of the 
light conductive means 40 and 42 comprises a plurality of light conductive 
elements arranged in alignment with each other at the end portion 34 in 
the longitudinal direction of the weft yarn 38 inserted, it is also 
possible to form only one of the light conductive means 40 and 42 of a 
plurality of light conductive elements arranged in alignment with each 
other at the end portion 34 similarly as mentioned above. 
Although each of the weft yarn sensors 20, 50, 56 and 60 is constructed 
such that the light conductive means 40 is located outer than the light 
conductive means 42 in the crescent portion 30 or in the upright and 
crescent portions 26 and 30, the each weft yarn sensor can be modified 
such that the light conductive means 40 is located inner than the light 
conductive means 42. 
Each of a light source and a light receiving device can be directly located 
at one of portions defining the gap in lieu of the provision of the light 
conductive means 40 and 42 or 54. 
It will be thus appreciated that the invention provides an improved weft 
yarn sensor in which the number of beam intercepted with a time lag by a 
weft yarn passing through the gap of the sensor body outside the aperture 
thereof is increased to at least two (2) and the time when the light fed 
to the light receiving device is intercepted by the weft yarn is increased 
to two times or more by the provision of reflector means producing at 
least one reflected beam so that changes in the quantity of light fed to 
the light receiving device and in the output of the light receiving device 
can be surely sensed and accordingly the performance of sensing the weft 
yarn is strikingly increased. 
It will be also appreciated that the invention provides an improved weft 
yarn sensor in which a concave mirror employed as a reflector produces a 
reflected light focussed at a predetermined position in the gap so that 
when the reflected light is intercepted by the weft yarn even if the 
diameter thereof is relatively fine, a change in the quantity of light fed 
to the light receiving device is more increased and a change in the output 
of the light receiving device is more surely sensed. 
It will be further appreciated that the invention provides an improved weft 
yarn sensor in which at least one of light projecting and receiving 
sections comprises a plurality of light conductive elements arranged in 
alignment with each other at one of portions of the sensor body defining 
the gap so that when the weft yarn intercepts the incident and/or 
reflected lights, a change in the light quantity is more increased and 
whether the weft yarn has been properly inserted or not can be surely 
sensed without being influenced by attaching of a fly fluff to the light 
projecting and/or receiving section.