BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a rapier loom for
weaving fabric by inserting a deft into a shed defined between warps by
using at least one rapier head moved reciprocatively through the shed.
More particularly, the present invention is concerned with a weft
insertion method and an apparatus for carrying out the same for a rapier
loom of the type mentioned above,
2. Description of Related Art
In the hitherto known rapier loom, fabric is woven by inserting a
weft into a shed defined between layers of warps (hereinafter also
referred to as an inter-warp shed) by using a feeding rapier head such as
one disclosed in Japanese Unexamined Patent Application Publication No.
195373/1993 (JP-A-5-195373). Parenthetically, the feeding rapier head is
referred to as the giver in the above publication. The weft inserted into
the inter-warp shed by means of the feeding rapier head is transferred to
a receiving rapier head (which is referred to as the taker in the above
publication). The weft transferred to the receiving rapier head is caused
to pass through the shed by retracting (i.e. , moving backwardly) the
receiving rapier head. Each of the feeding rapier head and the receiving
rapier head is constituted by a combination of a stationary gripper member
and a movable gripper member. For effectuating the transfer of the weft
from the feeding rapier head to the receiving rapier head, the latter is
positioned to a mid position substantially corresponding to a center of
the fabric being woven as viewed in the widthwise direction thereof in a
standby state in which the associated gripper members are opened. The
feeding rapier head releases the weft at the mid position mentioned above.
The weft as released is then gripped by the receiving rapier head. Thus,
the weft transfer between the feeding rapier head and the receiving rapier
head has been accomplished.
In the case of the copier loon disclosed in JP-A-5-195373, the
above-mentioned opening/closing operation of the rapier heads at the mid
position of the fabric as viewed in the direction widthwise thereof is
executed by a pair of levers constituting parts of a clamp opener disposed
underneath the fabric. More specifically, the clamp opener is driven by a
servo-motor which is controlled in conformance with movements of both the
rapier heads, each of which is also adapted to be driven by a servo-motor.
A driving system for driving controllably the clamp opener and the rapier
heads is adopted for the purpose of realizing the weft transfer from the
feeding rapier head to the receiving rapier head while avoiding the
possibility of injuring or damaging the weft.
However, the levers of the clamp opener for opening and closing
the rapier heads are so arranged as to enter the inter-warp shed space
from the underside of the lower warp layer by pushing aside the individual
warps. This motion of the clamp opener levers is carried out once for
every weft insertion shot or cycle. Thus, it is apparent that the warps
are likely to be injured as a result of frequent entrance and exit of the
clamp opener levers to and from the shed through the warp layer, which
gives rise to a problem in the conventional rapier loom.
SUMMARY OF THE INVENTION
In the light of the state of the art described above, it is an
object of the present invention to provide a weft insertion method for a
rapier loom which method is capable of inserting a weft into an inter-warp
shed by using a rapier head with high reliability and without injuring the
same.
It is another object of the present invention to provide a weft
inserting apparatus for carrying out the method mentioned above.
In view of the above and other objects which will become apparent
as the description proceeds, the present invention is directed to a rapier
loom for weaving a fabric by inserting a weft through a shed formed by
warps by using at least one rapier head constituted by a combination of a
stationary gripper member and a movable gripper member into said shed.
In the rapier loom mentioned above, there is provided according to
a general aspect of the present invention a weft insertion method which
features that the aforementioned movable gripper member is so implemented
as to respond to a magnetic force of a magnetic force exerting means to
thereby assume selectively a weft grip position and a weft release
position, that the magnetic force exerting means is changed over between a
first state in which the magnetic force exerting means exerts a magnetic
force to the movable gripper member and a second state in which the
magnetic force exerting means exerts no magnetic force to the movable
gripper member, and that the movable gripper member is positionally
changed over between the weft grip position and the weft release position
by switching the magnetic force exerting means between the first state and
the second state mentioned above, wherein the weft is gripped by the
movable gripper member when the movable gripper member is changed over
from the weft release position to the weft grip position, while the weft
is released when the movable gripper member is changed over from the weft
grip position to the weft release position.
In the weft insertion method described above, the movable gripper
member is disposed at the weft grip position when the magnetic force of
the magnetic force exerting means does not act on the movable gripper
member, while the magnetic force of the magnetic force exerting means acts
on the movable gripper member, the latter is disposed at the weft release
position. Thus, when the weft is to be gripped by the rapier head, the
movable gripper member is displaced (i.e., positionally changed over) to
the weft grip position from the weft release position. Upon reaching of
the movable gripper member at the weft grip position, the weft is gripped
between the stationary gripper member and the movable gripper member. On
the other hand, when the weft is to be released from the rapier head, the
movable gripper member is displaced to the weft release position from the
weft grip position. Upon reaching of the movable gripper member at the
weft release position, the weft is released from the state gripped or
grasped between the stationary gripper member and the movable gripper
member.
Upon transfer of the weft from the feeding rapier head to the
receiving rapier head, the latter waits for arrival of the receiving
rapier head at a weft transfer position, e.g. at a mid position as viewed
in the direction widthwise of the fabric being woven, while the movable
gripper member of the receiving rapier head is disposed at the weft
release position. Upon arrival of the feeding rapier head gripping the
weft at the weft transfer position, the movable gripper member of the
receiving rapier head is caused to assume the weft grip position,
whereupon the weft is gripped by the receiving rapier head, while the
movable gripper member of the feeding rapier head is positioned at the
weft release position, whereupon the weft gets rid of the `gripping action
of the feeding rapier head.
Further, provided according to a second aspect of the present
invention is a weft insertion method which features that the movable
gripper member is so implemented as to be responsive to a magnetic force
of electromagnetic means to thereby assume selectively a weft grip
position and a weft release position, and that the electromagnetic means
is changed over between a first state in which the electromagnetic means
exerts a magnetic force to the movable gripper member and a second state
in which the electromagnetic means exerts no magnetic force to the movable
gripper member, wherein upon application of the magnetic force, the
electromagnetic means is first applied with an over-excitation voltage,
which is then followed by application of a rated voltage. The movable
gripper member is positionally changed over between a weft grip position
and a weft release position by switching the electromagnetic means between
the first and second states mentioned above. The weft is gripped by the
movable gripper member by positionally switching the movable gripper
member from the weft release position to the weft grip position, while the
weft is released when the movable gripper member is changed over to the
weft release position from the weft grip position.
In the weft insertion method according to the second aspect of the
invention, the over-excitation voltage is first applied to the
electromagnet upon application of the magnetic force thereof to the
movable gripper member, which is then followed by application of the rated
voltage. Due to application of the over-excitation voltage, the
positional change-over of the movable gripper member from the weft grip
position to the weft release position is performed rapidly, whereby the
loom can be operated at an increased speed, to an advantage.
The present invention is also directed to be a rapier loom for
weaving a fabric by inserting a weft through a shed formed between warp
layers by inserting at least one rapier head constituted by a combination
of a stationary gripper member and a movable gripper member into the shed,
wherein a piezoelectric device is interposed between the stationary
gripper member and the movable gripper member.
In the rapier loom mentioned above, there is provided according to
a third aspect of the present invention a weft insertion method which
features that the piezoelectric device is switched between a first state
in which a voltage is applied to the piezoelectric device and a second
state in which no voltage is applied to the piezoelectric device, that the
movable gripper member is positionally changed over between a weft grip
position and a weft release position by switching the piezoelectric device
between the first and second states mentioned above, and that the weft is
gripped by the movable gripper member when it is changed over from the
weft release position to the weft grip position, while the weft is
released by positionally changing over the movable gripper member to the
weft release position from the weft grip position.
With the arrangement described above, the piezoelectric device
undergoes contraction and expansion in response to application of a
voltage thereto and clearing thereof. Thus, by controlling the voltage
application to the piezoelectric device, the positional change-over of the
movable gripper member between the weft grip position and the weft release
position can controllably be carried out.
As mentioned previously, the present invention is also concerned
with an apparatus for carrying out the weft insertion methods described
above. Thus, there is provided according to a further aspect of the
invention a weft inserting apparatus for the rapier loom described
hereinbefore, which apparatus features that the movable gripper member is
at least partially composed of a magnetic force responsive portion, and
that a magnetic force exerting means is installed at a position in the
vicinity of the weft insertion path, wherein the movable gripper member is
exchangeably positioned between a weft grip position and a weft release
position by switching the state of the magnetic force exerting means
between a first state in which magnetic force of the a magnetic force
exerting means acts on the magnetic force responsive portion of the
movable gripper member and a second state in which the magnetic force of
the magnetic force exerting means does not act on the magnetic force
responsive portion.
Further, for a rapier loom which includes a feeding rapier head
constituted by a stationary feeding gripper and a movable feeding gripper
and a receiving rapier head constituted by a stationary receiving gripper
and a movable receiving gripper, wherein both of the feeding rapier head
and the receiving rapier head are inserted into a shed formed by layers of
warps for inserting and passing a weft into and through the shed by
transferring the weft caught by the feeding rapier head to the receiving
rapier head, there is provided according to a further aspect of present
invention a weft inserting apparatus which features that it is comprised
of a first magnetic force responsive member constituting at least a
portion of the movable feeding gripper, a second magnetic force responsive
member constituting at least a portion of the movable receiving gripper, a
feeding magnetic force exerting means disposed in the vicinity of a weft
insertion dead center point located on a weft insertion path of the
feeding rapier head, a receiving magnetic force exerting means disposed at
a side of a weft insertion dead center point on a weft insertion path of
the receiving rapier head, a first switching means for switching the
feeding magnetic force exerting means between a first state in which a
magnetic force of the feeding magnetic force exerting means acts on the
magnetic force responsive member of the movable feeding gripper and a
second state in which the magnetic force of the feeding magnetic force
exerting means does not act on the magnetic force responsive member of the
movable feeding gripper to thereby change over the movable feeding gripper
between a weft grip position and a weft release position, and a second
means for switching the receiving magnetic force exerting means between a
first state in which a magnetic force of the receiving magnetic force
exerting means acts on the magnetic force responsive member of the movable
receiving gripper and a second state in which the magnetic force of the
receiving magnetic force exerting means does not act on the magnetic force
responsive member of the movable receiving gripper to thereby change over
the movable receiving gripper between a weft grip position and a weft
release position.
In a preferred mode for implementing the weft inserting apparatus
according to the present invention, a plurality of the feeding magnetic
force exerting means may be disposed in series to one another along the
weft insertion path of the feeding rapier head.
In another preferred mode for carrying out the invention, a
plurality of the receiving magnetic force exerting means may be disposed
in series to one another along the weft insertion path of the receiving
rapier head.
By virtue of the arrangements mentioned above, the feeding rapier
head undergoes sequentially the magnetic actions exerted by a plurality of
feeding magnetic force exerting means disposed in series along the weft
insertion path, while the receiving rapier head equally undergoes
sequentially the magnetic actions of plural receiving magnetic force
exerting means disposed serially along the weft insertion path. Thus, it
is possible to change over the rapier head between the weft releasing
state and the weft gripping state even when the rapier head is being
moved.
In yet another preferred mode for carrying out the present
invention, the magnetic force exerting means may be constituted by at
least one electromagnet, wherein the weft inserting apparatus may further
include a voltage application control means for controlling application of
a voltage to the electromagnet, an applied voltage level setting means for
setting a level of voltage applied to the electromagnet, a voltage
application timing setting means for setting a timing at which the voltage
is applied to the electromagnet.
In the weft inserting apparatus of the structure described above,
the timings at which the voltage is applied to the electromagnet is set at
the voltage application timing setting means, while the voltage
application control means commands the voltage application timings on the
basis of the data set at the voltage application timing setting means. On
the other hand, the voltage level setting means serves for setting the
level of voltage to be applied at the preset timings. In this case, the
voltage application timing control means as well as the timing/level
setting means may be implemented in the form of, for example, a
microcomputer.
In still another preferred mode for carrying out the present
invention, a buffer sheet of a soft material may be interposed between the
magnetic force exerting means and the movable gripper member such that
upon positioning of the movable gripper member at the weft release
position, the weft is gripped between the buffer sheet and the movable
gripper member.
According to a further aspect of the present invention, there is
provided for a rapier loom for weaving a fabric by inserting a weft
through a shed formed by layers of warps by inserting at least one rapier
head constituted by a combination of a stationary gripper member and a
movable gripper member into the shed, a weft inserting apparatus which
features that a piezoelectric device for driving the movable gripper
member is interposed between the movable gripper member and the stationary
gripper member, and that the movable gripper member is positionally
changed over between a weft grip position and a weft release position by
switching the piezoelectric device between a first state in which a
voltage is applied thereto and a second state in which no voltage is
applied thereto.
In the weft inserting apparatus of the structure described above,
changes in the length of the piezoelectric stack means in response to
application of a voltage and removal thereof is made use of for
positionally changing over the movable gripper member between the weft
grip position and the weft release position. The change-over mechanism as
well as the controller to this end can be implemented inexpensively in a
simplified structure while ensuring high reliability for the operation of
the weft inserting apparatus and hence that of the rapier loom.
The above and other objects, features and attendant advantages of
the present invention will more easily be understood by reading the
following description of the preferred embodiments thereof taken, only by
way of example, in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the course of the description which follows, reference is made
to the drawings, in which:
Fig. 1 is a partially broken-away front side view showing a weft
inserting apparatus for a rapier loom according to a first embodiment of
the present invention; Fig. 2 is an enlarged front side view showing schematically a
major portion of the weft inserting apparatus; Fig, 3 is a view similar to Fig. 2 and shows the major portion of
the weft inserting apparatus in a weft transferring state: Fig. 4 is a timing chart for illustrating application of voltages
to electromagnets employed in the weft inserting apparatus shown in Fig.
1; Fig. 5 is a vertical sectional view showing a modification in
respect to the disposition of the electromagnet; Fig. 6 is an enlarged front side view showing a major portion in a
weft inserting apparatus according to another embodiment of the present
invention; Fig. 7 is a view similar to Fig. 2 and shows a major portion of a
weft inserting apparatus for a rapier loom according to another embodiment
of the present invention; Fig. 8 is a timing chart for illustrating application of voltages
to electromagnets employed in the weft inserting apparatus shown in Fig.
5; Fig. 9 is a timing chart for illustrating application of voltages
to electromagnets employed in the weft inserting apparatus according to
another embodiment of the present invention; Fig. 10 is a timing chart for illustrating application of voltages
to electromagnets employed in the weft inserting apparatus according to
yet another embodiment of the present invention; Fig. 11 is a timing chart for illustrating application of voltages
to electromagnets employed in the weft inserting apparatus according to
still another embodiment of the present invention; Fig. 12 is a view similar to Fig. 2 and shows a major portion of a
weft inserting apparatus for a rapier loom according to a further
embodiment of the present invention; Fig. 13 is a view similar to Fig. 2 and shows a major portion of a
weft inserting apparatus for a rapier loom according to a still further
embodiment of the present invention; Fig. 14 is a view similar to Fig. 2 and shows a major portion of a
weft inserting apparatus for a rapier loom according to a yet further
embodiment of the present invention; Fig. 15 is a timing chart for illustrating application of voltages
to electromagnets employed in the weft inserting apparatus according to
another embodiment of the present invention; Fig. 16 is a partially broken-away enlarged sectional view showing
a structure of a piezoelectric device for driving a movable gripper member
according to a further embodiment of the present invention; and Fig. 17 is a view similar to Fig. 2 and shows a major portion of a
weft inserting apparatus for a rapier loom according to a further
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, the present invention will be described in detail in
conjunction with what is presently considered as preferred or typical
embodiments thereof by reference to the drawings. In the following
description, like reference characters designate like or corresponding
parts throughout the several views. Also in the following description, it
is to be understood that such terms as "left", "right", and the like are
words of convenience and are not to be construed as limiting terms.
At first, a weft insertion apparatus for a rapier loom according
to a first embodiment of the present invention will be described by
reference to Figs. 1 to 4, in which a reference numeral 1 denotes a
feeding rapier head which is adapted to be inserted into a shed defined
between layers of warps (not shown) from a weft insertion starting side,
and a numeral 2 denotes a receiving rapier head which is adapted to be
inserted into the shed from a weft insertion end or terminal side. The
feeding rapier head 1 and the receiving rapier head 2 are fixedly mounted
at both tip end portions of rapier bands 3 and 4 which are wound around
rapier wheels 5 and 6, respectively. The rapier wheels 5 and 6 are
reciprocatively rotated in the directions opposite to each other. More
specifically, the feeding rapier head 1 is inserted into the inter-warp
shed upon forward rotation (i.e., rotation in a given one direction) of
the rapier wheel 5, while the feeding rapier head 1 is retracted from the
shed upon backward rotation (i.e., rotation in the direction opposite to
the given one direction) of the rapier wheel 5. On the other hand, the
receiving rapier head 2 is inserted into the shed defined by the warps
upon forward rotation of the rapier wheel 6, while it is retracted upon
backward rotation thereof.
As shown in Figs. 3 and 4, the feeding rapier head 1 is
constituted by a combination of a stationary feeding gripper 7 made of a
non-magnetic material and a movable feeding gripper 8 of a magnetic
material. The stationary feeding gripper 7 is integrally formed with a
supporting member 7a, a gripping surface 7b and a position limiting member
7c. Fixedly mounted on the supporting member 7a are the movable feeding
gripper 8, a tip end portion of the rapier band 3 and a leaf spring 9 by
means of clamping screws 10. The movable feeding gripper 8 is made of a
metal material having a resiliency so as to serve as a spring. A gripping
surface 8a is formed at a tip end portion of the movable feeding gripper
8. The gripping surfaces 7b and 8a are adapted to be detachably brought
into contact with each other. The position limiting member 7c serves to
restrict or limit the downward displacement of the movable feeding gripper
8.
Again referring to Figs. 2 and 3, the receiving rapier head 2 is
constituted by a combination of a stationary receiving gripper 11 made of
a nonmagnetic material and a movable receiving gripper 12 of a magnetic
material. Coupled rotatably or swingably to the stationary receiving
gripper 11 is the movable receiving gripper 12 by means of a pivot 13.
The movable receiving gripper 12 is made of a metal material. Formed at
tip end portions of the stationary receiving gripper 11 and the movable
receiving gripper 12, respectively, are gripping surfaces 11a and 12a
facing oppositely to each other, The gripping surfaces 11a and 12a are
adapted to be detachably brought into contact with each other. A tip end
portion of the rapier band 4 is fixedly mounted on the movable receiving
gripper 12 by means of clamping screws 14. The stationary receiving
gripper 11 is integrally formed with a supporting member 11b and a
position limiting member 11c. A compression spring 15 is interposed
between the supporting member 11b and the movable receiving gripper 12.
The position limiting member 11c serves as a stopper for limiting a
downward movement of the movable receiving gripper 12.
The feeding rapier head 1 and the receiving rapier head 2 are
caused to move into the inter-warp shed upon forward rotations of the
rapier wheels 5 and 6, respectively, and encounter each other at a mid
position as viewed in the widthwise direction of a fabric being woven. On
the other hand, when the rapier wheels 5 and 6 are rotated in the reverse
or backward directions, respectively, the feeding rapier head 1 and the
receiving rapier head 2 are caused to retract from the shed defined by the
layers of warps. The position of the feeding rapier head 1 shown in Fig.
1 represents a position distanced at maximum from the inter-warp shed.
This position will be referred to as the retraction dead center point or
position. Similarly, the state of the receiving rapier head 2 shown in
Fig. 1 represents a position distanced maximally from the inter-warp shed.
This position will be referred to as the retraction dead center position
of the receiving rapier head 2.
The receiving rapier head 2 is adapted to run on and along a slay
17 which supports a reed 16. The running path of the receiving rapier
head 2, i.e., the weft insertion path, is so designed or determined as not
to interface with the reed 16 when it is retracted farthest from the cloth
fell of the fabric being woven. As can be seen in Fig. 1, electromagnets
18 and 19 are mounted at both end or terminal portions, respectively, of
the sley 17. More specifically, the electromagnet 18 is installed at a
position immediately below the weft insertion path for the feeding rapier
head 1, while the electromagnet 19 is installed at a position immediately
underneath the weft insertion path of the receiving rapier head 2.
Further, a pair of electromagnets 20 and 21 are embedded in the sley 17
substantially at mid portions thereof, respectively. In more concrete,
the electromagnet 20 is installed at a position immediately below the weft
insertion path of the feeding rapier head 1, while the electromagnet 21 is
disposed immediately beneath the weft insertion path of the receiving
rapier head 2.
A magnetic-field region over which the magnetic force of the
electromagnet 18 is active lies in the vicinity of the retraction dead
center position of the feeding rapier head 1, while a corresponding region
of the electromagnet 19 lies in the vicinity of the retraction dead center
position of the receiving rapier head 2. On the other hand, the magnetic-field
region of the electromagnet 20 lies in the vicinity of the position
at which the feeding rapier head 1 encounters the receiving rapier head 2,
i.e., a so-called weft insertion dead center position of the feeding
rapier head 1. On the other hand, the magnetic-field region of the
electromagnet 21 lies in the vicinity of the position at which the
receiving rapier head 2 encounters the feeding rapier head 1, i.e., the
weft insertion dead center position of the receiving rapier head 2. The
magnetic force of the electromagnet 18 acts on the movable feeding gripper
8 of the feeding rapier head 1 located in the vicinity of the retraction
dead center position, while that of the electromagnet 20 acts on the
movable feeding gripper 8 of the feeding rapier head 1 located in the
vicinity of the weft insertion dead center position. Similarly, the
magnetic force of the electromagnet 21 acts on the movable receiving
gripper 12 of the receiving rapier head 2 located in the vicinity of the
weft insertion dead center position thereof.
Under the influence of the magnetic forces of the electromagnets
18 and 20, the movable feeding gripper 8 is caused to bend or angularly
move toward the electromagnets 18 and 20 around a fulcrum defined by the
supporting member 7a against their own resiliences and that of the leaf
spring 9. Due to this angular displacement, the movable feeding gripper 8
is positionally changed over to a weft release position shown in Fig. 3
from a weft grip position shown Fig. 2. The downward movement of the
movable feeding gripper 8 is limited by the position limiting member 7c.
In the state where the downward movement of the movable feeding gripper 8
is stopped by the position limiting member 7c, the movable feeding gripper
8 assumes a position closest to the electromagnet 18 or 20. However, the
warps are positively prevented from being sandwiched between the movable
feeding gripper 8 and the electromagnet 18; 20 and thus protected against
any injury.
Similarly, under the influence of the magnetic forces of the
electromagnets 19 and 21, the movable receiving gripper 12 is caused to
bend or angularly move toward the electromagnets 19 and 21 around the
pivot pin 13 against the spring force of the compression spring 15. Due
to this angular displacement, the movable receiving gripper 12 is
positionally changed over to a weft release position shown in Fig. 3 from
a weft grip position shown Fig. 2. The downward movement of the movable
receiving gripper 12 is limited by the stopper or position limiting member
11c. In the state where the downward movement of the movable receiving
gripper 12 is limited by the position limiting member 11c, the movable
receiving gripper 12 assumes a position closest to the electromagnet 19 or
21. However, the warps are positively prevented from being sandwiched
between the movable receiving gripper 12 and the electromagnet 19; 21 and
thus protected against any injury.
As can be seen from Fig. 1, the electromagnets 18, 19, 20 and 21
which serve as magnetic force exerting means are electrically energized
through the driving circuits 22, 23, 24 and 25, respectively, under the
control of a control computer C. More specifically, the driving circuits
22 to 25 serving as applied voltage setting means apply a rated voltage V0
to the electromagnets 18, 19, 20, 21, respectively. On the other hand,
the control computer (or computerized controller, to say in another way) C
serving as the voltage application control means is equipped with a
voltage application timing setting unit 27 and a rotary encoder 28. The
voltage application timing setting unit 27 serves for inputting to the
control computer C the voltage application timing control signals for the
electromagnets 18 to 21, respectively. On the other hand, the rotary
encoder 28 serves for detecting rotational angles or angular positions of
the loom. On the basis of the loom rotation angle information available
from the output of the rotary encoder 28, the control computer C issues
commands to the driving circuits 22 to 25 applications of the rated
voltage V0, in response to which the driving circuits 22 to 25 apply the
rated voltage V0 to the electromagnets 18 to 21 at the preset timings,
respectively.
Referring to Fig. 4, a waveform D1 represents an amplitude and a
timing of a voltage applied to the electromagnet 18, while a waveform D2
represents an amplitude and a timing of a voltage applied to the
electromagnet 19. Further, a waveform E1 represents an amplitude and a
timing of a voltage applied to the electromagnet 20, while a waveform E2
represents an amplitude and a timing of a voltage applied to the
electromagnet 21. In the timing chart shown in Fig. 4, the voltage V is
taken along the ordinate with a rotation angle (or angular position) of
the loom being taken along the abscissa. Each of the voltages represented
by the waveforms D1, D2, E1 and E2 is a rated voltage V0. The timings
Td1, Td2, Te1 and Te2 at which the rated voltage V0 is applied are set by
the voltage application timing setting unit 27 to be subsequently inputted
to the control computer C. The control computer C issues voltage
application commands to the driving circuits 22 to 25 on the basis of the
angular position information of the loom as detected by the rotary encoder
28 and the information concerning the voltage application timings Td1,
Td2, Te1 and Te2, as supplied from the timing setting unit 27. In
response to the voltage application commands mentioned above, the driving
circuits 22 to 25 apply the rated voltage V0 to the electromagnets 18 to
21, respectively.
When the voltage of the waveform D1 is applied, the position of
the movable feeding gripper 8 of the feeding rapier head 1 is changed over
to the weft release position from the weft grip position. The feeding
rapier head 1 then starts the weft insertion in the state in which the
movable feeding gripper 8 is disposed at the weft release position. The
position of the movable feeding gripper 8 is changed over from the weft
release position to the weft grip position in the vicinity of the
retraction dead center position. Through the positional change-over
mentioned above, the weft Y is retained between the gripping surfaces 7b
and 8a of the feeding grippers 7 and 8, respectively, of the feeding
rapier head 1. The feeding rapier head 1 takes up the weft Y at a weft
take-up position in the vicinity of the retraction dead center position,
whereby the weft Y is inserted into the shed. The electromagnet 18 serves
as the weft take-up magnetic means.
As shown in Fig. 2, the receiving rapier head 2 arrives at the
weft insertion dead center position in precedence to the feeding rapier
head 1. The movable receiving gripper 12 of the receiving rapier head 2
arrived at the weft insertion dead center position is changed over from
the weft grip position to the weft release position in response to
application of the voltage represented by the waveform E2. The receiving
rapier head 2 then waits for arrival of the feeding rapier head 1 in the
state in which the movable receiving gripper 12 is disposed at the weft
release position. The weft Y retained by the feeding rapier head 1 arrived
at the weft insertion dead center position is transferred to the receiving
rapier head 2 to be thereby positioned between the gripping surfaces 11a
and 12a thereof. When the weft Y is positioned to lie between the
gripping surfaces 11a and 12a, the voltage application to the
electromagnet 21 is interrupted, which results in that the movable
receiving gripper 12 is changed over to the weft grip position from the
weft release position. Through this positional change-over, the weft Y is
now retained between the gripping surfaces 11a and 12a of the receiving
rapier head 2, as can be seen in Fig. 3. The movable feeding gripper 18
of the feeding rapier head 1 arrived at the weft insertion dead center
position is changed over from the weft grip position to the weft release
position in response to application of the voltage represented by the
waveform E1. As a consequence, the weft Y gets rid of the gripping action
of the feeding rapier head 2. Thus, it can be said that the electromagnet
20 serves as the feeding magnetic force exerting means, while the
electromagnet 21 serves as the receiving magnetic force exerting means.
Subsequently, both the feeding rapier head 1 and the receiving
rapier head 2 are moved backwardly or retracted toward the respective
retraction dead center positions, whereby the weft Y held by the receiving
rapier head 2 is caused to extend through the inter-warp shed. The
movable receiving gripper 12 of the receiving rapier head 2 arrived at the
weft release position located immediately before the retraction dead
center position is changed over from the weft grip position to the weft
release position in response to application of the voltage represented by
the waveform D2. As a consequence, the weft Y gets rid of the gripping
action of the receiving rapier head 2. Thus, it can be said that the
electromagnet 21 serves as the weft releasing magnetic force exerting
means. Subsequently, the reed 16 starts beating operation from the most
retracted position thereof.
As will be appreciated from the above description, positions of
the movable grippers 8 and 12 of the rapier heads 1 and 2, respectively,
are changed over from the weft grip position to the weft release position
under the action of the electromagnets 18 to 21. Upon disappearance of
influence of the magnetic force, the movable grippers 8 and 12 are changed
over from the weft release position to the weft grip position under the
influence of the spring forces. The driving forces for positionally
changing over the movable grippers 8 and 12 between the weft grip position
and the weft release position are provided by the magnetic forces
generated by the electromagnets 18 to 21 and the spring forces of the
rapier heads 1 and 2 themselves. Thus, the mechanism for positionally
changing over the movable grippers 8 and 12 between the weft grip position
and the weft release position will never provide interference to the
warps, which in turn means that the warps can positively be protected from
injury upon operations of the rapier heads 1 and 2.
The arrangement for positively actuating the movable grippers 8
and 12 under the action of the magnetic forces makes it possible to ensure
the optimal timings for open/close operations of the rapier heads 1 and 2,
whereby setting of the optimal timings for the gripping and release
operations of the weft Y can be facilitated. On the other hand, easiness
in setting the optimal timings for gripping and releasing of the weft Y
can ensure reliable taking-up of the weft Y by the feeding rapier head 1
as well as reliable transfer of the weft Y from the feeding rapier head 1
to the receiving rapier head 2. Certainly, the weft Y may also be caught
without opening and closing the feeding rapier head 1. It should however
be mentioned that the arrangement that the weft Y is introduced into
between the gripping surfaces 7b and 8a in the state where the movable
feeding gripper 8 is disposed at the weft release position and then the
movable feeding gripper 8 is disposed at the weft grip position is more
reliable when compared with the arrangement of catching the weft Y with
the feeding rapier head 1 in the closed state thereof. At this juncture,
it should also be added that the timing at which the weft Y is released
from the feeding rapier head 1 exerts influence to the final insertion
posture or state of the weft Y, which in turn affects the quality of the
fabric. Besides, easiness of setting the optimal timing for the release
of the weft Y from the feeding rapier head 1 contributes to improvement of
the fabric quality.
The electromagnets 18 and 20 installed on the slay 17 and the
movable feeding gripper 8 of the feeding rapier head 1 are positioned
mutually very closely every time the magnetic forces of the electromagnets
16 and 20 become active. Thus, the magnetic forces of the electromagnets
18 and 20 can effectively act on the movable feeding gripper 8.
Similarly, the electromagnets 19 and 21 mounted on the slay 17 and the
movable receiving gripper 12 of the receiving rapier head 2 are positioned
mutually very closely upon activation of the electromagnets 19 and 21.
Thus, the magnetic forces of the electromagnets 19 and 21 can effectively
act on the movable receiving gripper 12. Furthermore, by setting properly
the resiliency of the movable feeding gripper 8 itself and the spring
force of the leaf spring 9, the movable feeding gripper 8 can be changed
over to the weft grip position from the weft release position at a high
speed. Similarly, by setting appropriately the spring force of the
compression spring 15, it is possible to change over the movable receiving
gripper 12 from the weft release position to the weft grip position at a
high speed. In this conjunction, it should be noted that the resiliency
of the movable feeding gripper 8 itself and the spring force of the leaf
spring 9 are selected to be sufficiently large for gripping the weft Y
without fail. Similarly, the spring force of the compression spring 15 is
set large enough to grip the weft with reliability. The amplitude of the
rated voltage V0 is so selected as to be capable of changing over the
movable grippers 8 and 12 from the weft grip position to the weft release
position against the spring force mentioned above.
Thus, by combining appropriately the preset magnetic forces and
spring forces, the change-over of the movable grippers 8 and 12 between
the weft grip position and the weft release position can be effected at a
high speed. Further, interposition of the leaf spring 9 in the manner
mentioned previously facilitates the setting of the desired spring force.
In this conjunction, adjustment of the spring force of the leaf spring 9
can easily be realized by changing the number of the leaf springs 9 or the
length thereof. It goes without saying that the high-speed positional
change-over of the movable grippers 8 and 12 between the weft grip
position and the weft release position allows the loom to operate at a
high rotation speed.
The apparatus for opening and closing the rapier heads 1 and 2 by
using the electromagnets 18 to 21 according to the instant embodiment of
the present invention can be implemented in a simplified structure of a
compact size when compared with the clamp opener apparatus disclosed in
JP-A-5-195373 mentioned previously. With the structure of the prior art
clamp opener, the lever for opening and closing the rapier head is brought
into direct contact with the rapier head. Consequently, both the lever
and the rapier head undergo friction and abrasion, which results in error
in the opening degree of the rapier head as well as the timings at which
it is opened and closed. Besides, heat generated due to the friction
impairs the precision of the parts constituting the rapier head. Of
course, abrasion of the rapier head and deviation of precision of the
parts provide obstruction to reliable transfer of the weft Y from the
feeding (giver) rapier head to the receiver (taker) rapier head. By
contrast, in the case of the apparatus according to the instant embodiment
of the invention, the movable grippers 8 and 12 are changed over
contactless between the weft grip position and the weft release position.
Thus, neither abrasion nor aberrations in the precision of the parts due
to the direct contact open/close operation can take place.
Furthermore, clearance between the rapier heads 1 and 2 running on
the top surface of the sley 17 is realized with high accuracy.
Accordingly, the structure in which the electromagnets 18 to 21 are
installed on the sley 17 increases the accuracy of clearance between the
electromagnets 18 to 21 and the movable grippers 8 and 12. It is self-explanatory
that such high accuracy of clearance between the
electromagnets 18 and 21 and the movable grippers 8 and 12 is very
advantageous in realizing the high-speed positional change-over of the
movable grippers 8 and 12 between the weft grip position and the weft
release position.
Now, another embodiment of the present invention will be described
by reference to Figs. 5 and 6. As is shown in Fig. 6, the sley in the
weft inserting apparatus according to the instant embodiment is divided
into three sley members 17a, 17b and 17c at a mid portion as viewed in the
direction widthwise of the fabric. The individual sley members 17a, 17b
and 17c are supported via sley swords 29 on a rocking shaft 30 (see Fig.
5) which is adapted to be reciprocatively rocked or swung by a reed
driving mechanism (not shown). There are mounted electromagnets 18 and 19
at lateral sides of the sley members 17a and 17c, respectively. An
electromagnet 20 is interposed between the sley members 17a and 17b with
another electromagnet 21 being interposed between the sley members 17b and
17c. Each of the electromagnets 18 to 21 is supported on a breast beam 32
by way of a bracket 31. Parenthetically, the breast beam 32 is employed
for supporting a fell plate serving for preventing the downward
displacement of a fabric (not shown), a temple device for preventing
shrinkage of fabric and an expansion bar, wherein very high accuracy is
ensured for the positional relation between the sley 17 and the breast
beam 32. Thus, clearances between the electromagnets 18 to 21 supported
on the breast beam 32 and the movable grippers 8 and 12 of the rapier
heads 1 and 2 can easily be realized with high accuracy. Besides, because
the electromagnets 18 to 21 and electric wires therefor are provided
fixedly, possibility of breakage of the wires and occurrence of failure in
the electromagnets 18 to 21 can positively be suppressed. Additionally,
the sley 17 as a whole can be implemented in light weight, which is very
beneficial for increasing the beating operation speed.
Another embodiment of the weft inserting apparatus according to
the present invention will be described by reference to Figs. 7 and 8. In
these drawings. Fig. 7 will also be referenced in the description of other
embodiments shown in Figs. 8 to 10. In the weft inserting apparatus
according to the instant embodiment of the invention, a movable feeding
gripper 8A of the feeding rapier head 1 is comprised of a non-magnetic
member 8b and a magnetic member 8c disposed to face in opposition to the
electromagnet. Similarly, a movable receiving gripper 12A of the
receiving rapier head 2 is comprised of a non-magnetic member 12b and a
magnetic member 12c with the magnetic member 12c positioned to face
oppositely to the electromagnet. The non-magnetic members 8b and 12b may
preferably be made of a resin material with the magnetic members 8c and
12c being formed of a metal material with a view to implementing the
rapier heads 1 and 2 in light weight. Needless to say, a light-weight
structure of the rapier heads 1 and 2 is advantageous in that they can be
moved or operated with an increased speed.
The positions at which the electromagnets 18 to 21 are mounted are
same as in the case of the weft inserting apparatus according to the first
embodiment of the invention. Driving circuits 22A, 23A, 24A and 25A for
electrically energizing the electromagnets 18 to 21, respectively, are
each designed for outputting either one of the rated voltage V0 and the
over-excitation voltage V1 in response to a command issued by the control
computer C. Referring to Fig. 8, a waveform D3 represents an amplitude
and a timing of a voltage applied to the electromagnet 18, while a
waveform D4 represents an amplitude and a timing of a voltage applied to
the electromagnet 19. Further, a waveform E3 represents an amplitude and
a timing of a voltage applied to the electromagnet 20, while a waveform E4
represents an amplitude and a timing of a voltage applied to the
electromagnet 21. Each of the voltages represented by the waveforms D3,
D4, E3 and E4 has a rated voltage level V0 and an over-excitation voltage
level V1. The timings Td03, Td04, Te03 and Te04 at which the rated
voltage V0 is applied as well as the timings Td13, Td14, Te13 and Te14 at
which the over-excitation voltage V1 is applied are set by the voltage
application timing setting unit 27 and inputted to the control computer C.
The control computer C issues voltage application commands for applying
the rated voltage V0 or the over-excitation voltage V1 to the driving
circuits 22A to 25A on the basis of angular position information of the
loom as detected by the rotary encoder 28 and the information concerning
the voltage application timings mentioned above. In response to the
voltage application commands mentioned above, the driving circuits 22A to
25A apply the rated voltage V0 and the over-excitation voltage V1 to the
electromagnets 18 to 21, respectively, at such timings the illustrated in
Fig. 8.
Upon application of the magnetic forces of the electromagnets 18
and 20 to the magnetically responsive movable feeding gripper 8A as well
as upon application of the magnetic forces of the electromagnets 19 and 21
to the magnetically responsive receiving gripper 12A, the over-excitation
voltage V1 is first applied to the electromagnets 18; 20 and the
electromagnets 19; 21. In succession to application of the over-excitation
voltage V1, the rated voltage V0 is applied. In response to
application of the over-excitation voltage V1, the movable grippers 8A and
12A are rapidly changed over to the weft release position from the weft
grip position. It is self-explanatory that the rapid change-over of the
movable grippers 8A and 12A makes it possible to operate the loom at an
increased speed.
Now, description will be directed to the weft inserting apparatus
according to another embodiment of the invention by referring to Figs. 7
and 9. In the case of the weft inserting apparatus now under
consideration, the movable feeding gripper 8B of the feeding rapier head 1
is comprised of a non-magnetic member 8b and a permanent magnet 8d,
wherein the permanent magnet 8d is disposed in opposition to the
electromagnet. Similarly, the movable receiving gripper 12B of the
receiving rapier head 2 is composed of a non-magnetic member 12b and a
permanent magnet 12d which is disposed in opposition to the electromagnet.
The positions at which the electromagnets 18 to 21 are installed are same
as those of the weft inserting apparatus described hereinbefore in
conjunction with the first embodiment of the invention.
The driving circuits 22B, 23B, 24B and 25B for electrically
energizing the electromagnets 18 to 21, respectively, are each designed
for outputting either one of the rated voltage (+)V0 of plus polarity and
the rated voltage (-)V0 of minus polarity in response to a command issued
by the control computer C. Referring to Fig. 9, a waveform D5 represents
amplitudes and timings of voltages applied to the electromagnet 18, while
a waveform D6 represents amplitudes and timings of voltages applied to the
electromagnet 19. Further, a waveform E5 represents amplitudes and
timings of voltages applied to the electromagnet 20, while a waveform E6
represents amplitudes and timings of voltages applied to the electromagnet
21. The timings (+)Td5, (+)Td6, (+)Te5 and (+)Te6 at which the positive
rated voltage (+)V0 is applied as well as the timings (-)Td5, (-)Td6,
(-)Te5 and (-)Te6 at which the negative rated voltage (-)V0 is applied are
set by the voltage application timing setting unit 27 to be inputted to
the control computer C. The control computer C issues voltage application
commands for applying the positive rated voltage (+)V0 or the negative
rated voltage (-)V0 to the driving circuits 22B to 25B on the basis of
angular position information of the loom as obtained from the output of
the rotary encoder 28 and the information concerning the voltage
application timings mentioned above. In response to the voltage
application commands mentioned above, the driving circuits 22B to 25B
apply the rated voltage (+)V0 of plus polarity or the rated voltage (-)V0
of minus polarity to the electromagnets 18 to 21, respectively, at the
timings illustrated in Fig. 9.
The movable feeding gripper 8B is held at the weft grip position
under the resiliency of the movable feeding gripper 8B and the spring
force of the leaf spring 9 when no magnetic forces of the electromagnets
18 and 20 are exerted. Similarly, the movable receiving gripper 12B are
held at the weft grip position under the spring force of the compression
spring 15 when neither the electromagnet 19 nor the electromagnet 21 are
active. The magnetic force as generated upon application of the rated
voltage (+)V0 of plus polarity acts as a magnetic attracting force for the
movable grippers 8B and 12B, while the magnetic force generated upon
application of the rated voltage (-)V0 of minus polarity acts as a
repulsing magnetic force. In response to the magnetic attracting force
generated upon application of the rated voltage (+)V0 of plus polarity,
the movable gripper 8B or 12B is positionally shifted to the weft release
position from the weft grip position. On the other hand, in response to
the magnetic repulsing force generated upon application of the rated
voltage (-)V0 of minus polarity, the movable gripper 8B or 12B is shifted
to the weft grip position from the weft release position. In this manner,
the positional changing-over of the movable grippers 8B and 12B to the
weft grip position from the weft release position is effected by
electrically energizing the electromagnets 18 to 21 in the manner
described above. For this reason, so far as the feeding rapier head 1 is
concerned, magnitude of the spring force for gripping or grasping the weft
under the resiliency of the movable feeding gripper 8B itself and that of
the leaf spring 9 may be reduced to a necessary minimum. The same holds
true for the spring force of the compression spring 15 for allowing the
receiving rapier head 2 to grip the weft. By selecting the resiliency of
the movable feeding gripper 8B and the spring force of the leaf spring 9
as small as possible in this manner, the positional change-over of the
movable feeding gripper 8B to the weft release position from the weft grip
position can be accomplished with an increased speed. Similarly, by
selecting the spring force of the compression spring 15 as small as
possible, the positional shift of the movable receiving gripper 12B to the
weft release position from the weft grip position can be realized at an
enhanced speed.
Next, description will be directed to a weft inserting apparatus
according to another embodiment of the invention by reference to Figs. 7
and 10. In the case of the weft inserting apparatus according to the
instant embodiment, the movable feeding gripper 8B of the feeding rapier
head 1 is comprised of a non-magnetic member 8b and a permanent magnet 8d,
wherein the permanent magnet 8d is so disposed as to face in opposition to
the electromagnet. Similarly, the movable receiving gripper 12B of the
receiving rapier head 2 is composed of a non-magnetic member 12b and a
permanent magnet 12d which is disposed in opposition to the electromagnet.
The positions at which the electromagnets 18 to 21 are installed are same
as those of the weft inserting apparatus described hereinbefore in
conjunction with the first embodiment.
The driving circuits 22C, 23C, 24C and 25C for electrically
energizing the electromagnets 18 to 21, respectively, are each designed
for outputting either one of the rated voltage (+)V0 of plus polarity, the
rated voltage (-)V0 of minus polarity, the over-excitation voltage (+)V1
of plus polarity and the over-excitation voltage (-)V1 of minus polarity
in response to a command issued by the control computer C. Referring to
Fig. 10, a waveform D7 represents amplitudes and timings of voltages
applied to the electromagnet 18, while a waveform D8 represents amplitudes
and timings of voltages applied to the electromagnet 19. Further, a
waveform E7 represents amplitudes and timings of voltages applied to the
electromagnet 20, while a waveform E8 represents amplitudes and timings of
voltages applied to the electromagnet 21. The timings (+)Td07, (+)Td08;
(+)Te07, (+)Te08 at which the positive rated voltage (+)V0 is applied as
well as the timings (-)Td07, (-)Td08; (-)Te07, (-)Te08 at which the
negative rated voltage (-)V0 is applied are set by the voltage application
timing setting unit 27 to be subsequently loaded to the control computer
C. Similarly, the timings (+)Td17, (+)Td18; (+)Te17, (+)Te18 at which the
over-excitation voltage (+)V1 of plus polarity is applied as well as the
timings (-)Td17, (-)Td18; (-)Te17, (-)Te18 at which the over-excitation
voltage (-)V1 of minus polarity is applied are preset by the voltage
application timing unit 27 and inputted to the control computer C. The
control computer C issues voltage application commands for applying the
rated voltage (+)V0 of plus polarity, the rated voltage (-)V0 of minus
polarity, the over-excitation voltage (+)V1 of plus polarity or the over-excitation
voltage (-)V1 of minus polarity to the driving circuit 22C; 25C
on the basis of the angular position information of the loom as obtained
from the output of the rotary encoder 28 and the information concerning
the voltage application timings mentioned above. In response to the
voltage application commands mentioned above, the driving circuits 22C to
25C apply selectively the rated voltage (+)V0 of plus polarity, the rated
voltage (-)V0 of minus polarity, the over-excitation voltage (+)V1 of plus
polarity or the over-excitation voltage (-)V1 of minus polarity to the
electromagnets 18 to 21, respectively, at such timings as illustrated in
Fig. 10.
In the weft inserting apparatus according to the instant
embodiment of the invention, there can equally be obtained similar
advantageous effects as mentioned previously in conjunction with the
embodiment illustrated in Figs. 8 and 9. Additionally, because the over-excitation
voltage is applied when the movable feeding gripper 8B or the
movable receiving gripper 12B is to be changed over from the weft release
position to the weft grip position as well, transition of the movable
gripper 8B or 12B to the weft grip position from the weft release position
can be realized at a further increased speed. Of course, the high-speed
positional change-over of the movable feeding gripper 8B and the movable
receiving gripper 12B from the weft release position to the weft grip
position contributes to a high-speed operation of the loom, Among others,
the high-speed operation of the movable feeding gripper 8B for allowing
the feeding rapier head 1 to catch the weft is very effective for speeding
up the weft insertion starting operation of the feeding rapier head 1.
Figure 11 shows a version of the weft inserting apparatus in which
the movable grippers 8B and 12B additionally provided with the permanent
magnets 8d and 12d are adopted. When the movable feeding gripper 8B or
the movable receiving gripper 12B is shifted to the weft grip position
from the weft release position, the over-excitation voltage (+)V1 of plus
polarity is applied first, as is represented by the waveforms D9, D10, E9,
E10. However, when the movable feeding gripper 8B or the movable
receiving gripper 12B is to be changed over from the weft release position
to the weft grip position, only the rated voltage (-)V0 of minus polarity
is applied. By making use of the over-excitation voltage (+)V1 of plus
polarity upon changing-over of the movable feeding gripper 8B or the
movable receiving gripper 12B from the weft release position to the weft
grip position, resiliency of the movable grippers 8B and 12B as well as
the spring forces of the leaf spring 9 and the compression spring 15 can
be increased, which in turn enables the movable feeding gripper 8B or the
movable receiving gripper 12B to be shifted from the weft release position
to the weft grip position at an increased speed.
Next, description will turn to the weft inserting apparatuses
according to yet further embodiments of the present invention by reference
to Figs. 12 and 13. In the case of these embodiments, the position
limiting members 7c and 11c are spared in the stationary grippers 7 and 11
of the rapier heads 1 and 2, respectively. Instead thereof, buffer sheets
33 of a soft material such as moquette are secured to the sley 17 and the
electromagnets 20 and 21 in the case of the embodiment shown in Fig. 12,
while in the apparatus shown in Fig. 13, the buffer sheets 33 are fixedly
mounted only on the electromagnets 18 to 21, respectively. When the
movable feeding gripper 8A (or 8B) and the movable receiving gripper 12A
(or 12B) are located at the weft release position, the warps are gripped
between the movable gripper 8A (or 8B); 12A (or 12B) and the buffer sheet
33. In that case, the buffer sheet 33 functions to prevent the warps
sandwiched between the movable gripper 8A (or 8B); 12A (or 12B) and the
electromagnet from being injured. It should further be mentioned that
omission of the position limiting members 7c and 11c contributes to lightweight
implementation of the rapier heads 1 and 2.
Parenthetically, it should also be added that in place of using
the moquette for forming the buffer sheet 33, the latter may be made of a
sheet material such as of a synthetic resin, woven fabric, leather or the
like.
Next, another embodiment of the present invention will be
described by reference to Figs. 14 and 15. In the weft inserting
apparatus according to the instant embodiment, a plurality of (three in
this case) electromagnets 20A, 20B and 20C are disposed along the weft
insertion path in the vicinity of the weft insertion dead center position.
Furthermore, a plurality of (three in this case) electromagnets 21A, 21B
and 21C are disposed along the weft insertion path in the vicinity of the
weft insertion dead center position of the receiving rapier head 2. The
electromagnets 20A, 20B and 20C serve as the weft feeding magnetic force
exerting means, while the electromagnets 21A, 21B and 21C serve as the
weft receiving magnetic force exerting means. As the movable grippers of
the feeding rapier head 1, the movable feeding gripper 8A or 8B shown in
Fig. 7 is employed, while as the movable gripper for the receiving rapier
head 2, the movable receiving gripper 12A or 12B is used.
A waveform E11 shown in Fig. 15 indicates an amplitude and
application timing of the rated voltage applied to the electromagnet 20A
by a driving circuit 24D1. On the other hand, a waveform E12 shown in the
same figure indicates an amplitude and application timing of the rated
voltage applied to the electromagnet 20B by a driving circuit 24D2.
Further, a waveform E13 indicates a magnitude and application timing of
the rated voltage applied to the electromagnet 20C by a driving circuit
24D3, while a waveform E14 indicates a magnitude and application timing of
the rated voltage applied to the electromagnet 21A by a driving circuit
25E1. Furthermore, a waveform E15 indicates a magnitude and application
timing of the rated voltage applied to the electromagnet 21B by a driving
circuit 25E2, while a waveform E16 indicates a magnitude and application
timing of the rated voltage applied to the electromagnet 21C by a driving
circuit 25E3. Energization/deenergization of the electromagnets 20A, 20B
and 20C is performed in a relaying manner, so to say. Similarly,
energization/deenergization of the electromagnets 21A, 21B and 21C is
carried out in a relaying manner. The energization/deenergization of the
electromagnets 20A, 20B and 20C in a relaying manner makes it possible to
change over the position of the movable feeding gripper 8A (or 8B) between
the weft grip position and the weft release position in the course of
moving of the feeding rapier head 1. Equally, the energization and
deenergization of the electromagnets 21A, 21B and 21C in the relaying
fashion permits the positional change-over of the movable receiving
gripper 12A (or 12B) between the weft grip position and the weft release
position even when the receiving rapier head 2 is moving. Thus, even in
the case where the weft insertion is performed through cooperation of the
rapier heads 1 and 2 within a short time, there can be ensured a
sufficient time for effecting the positional shifts of the movable feeding
gripper 8A (or 8B) and the movable receiving gripper 12A (or 12B) between
the weft grip position and weft release position, respectively. At this
juncture, it should be noted that availability of a sufficient time for
the positional change-over of the movable feeding gripper 8A (or 8B) and
the movable receiving gripper 12A (or 12B) can enhance the reliability of
the weft transfer operation from the feeding rapier head 1 to the
receiving rapier head 2.
As a modification of the weft inserting apparatus according to the
instant embodiment of the invention, the voltage of minus polarity may be
applied to the electromagnet in succession to a application of the voltage
of plus polarity when the movable feeding gripper 8B and the movable
receiving gripper 12B are employed, In that case, there can be obtained
advantageous effects similar to those described previously in conjunction
with the embodiment shown in Fig. 9. As another modification, the
energization/deenergization of the electromagnets in the relaying fashion
may be performed only for the operation of the feeding rapier head 1 or
alternatively only for the operation of the receiving rapier head 2.
Finally, description will turn to yet another embodiment of the
present invention by reference to Figs. 16 and 17. In the case of the
weft inserting apparatus now under consideration, the feeding rapier head
1 is implemented by securing fixedly a base end portion of a flexible
movable feeding gripper 8C to the stationary feeding gripper 7A. A
piezoelectric device 35 is interposed between the stationary feeding
gripper 7A and the movable feeding gripper 8C. On the other hand, the
receiving rapier head 2 is implemented in such a structure in which a base
end portion of a flexible movable feeding gripper 8C is secured to the
stationary receiving gripper 11A. Equally, a piezoelectric device 36 is
interposed between the stationary receiving gripper 11A and the movable
receiving gripper 12C. Electric wires connected to the piezoelectric
devices 35 and 36 are laid down along the rapier bands 3 and 4,
respectively.
As is shown in Fig, 16, the piezoelectric device 35 (or 36) is
realized in such a structure in which piezoelectric elements 35a (or 36a)
are stacked alternately with electric conductors 35b (or 36b) with the
piezoelectric element 35a (or 36a) being sandwiched between the conductors
35b (or 36b). One of the electric conductors 35b and 36b sandwiching the
piezoelectric element 35a or 36a is connected to an electrode of plus
polarity of a power source while the other is connected to the electrode
of minus polarity. Upon application of a voltage to the piezoelectric
device 35 or 36, the piezoelectric element 35a or 36a expands in the
stacking direction, which results in that the piezoelectric device 35 or
36 as a whole expands. The movable feeding gripper 8C of the feeding
rapier head is disposed at the weft grip position upon voltage application
to the piezoelectric device 35 and changed over to the weft release
position in response to clearing of the applied voltage. On the other
hand, the movable receiving gripper 12C of the receiving rapier head is
disposed at the weft grip position in response to the voltage application
to the piezoelectric device 36 and shifted to the weft release position
when the voltage applied to the piezoelectric device 36 is cleared.
Although the expansion/contraction of the piezoelectric devices 35, 36 is
small, deformation or vibration of the piezoelectric devices 35, 36 is
magnified due to lever-like implementation of the flexible movable feeding
gripper 8C as well as that of the movable receiving gripper 12C, whereby
expansion/contraction of the piezoelectric device 35 or 36 is translated
to effective displacement of the gripping surfaces 8a and 12a.
The driving force for changing over the movable gripper 8C or 12C
between the weft grip position and the weft release position originates in
the expansion/contraction of the piezoelectric device 35 or 36. Thus, the
mechanism for changing over the movable gripper 8C or 12C between the weft
grip position and the weft release position is positively prevented from
interfering with the warp. To say in another way, the warps can
positively be protected against injury or damage due to the switching
operations of the feeding rapier head 1 and the receiving rapier head 2.
The structure in which the movable gripper 8C or 12C is positively
moved in response to the expansion/contraction of the piezoelectric device
35 or 36 facilitates setting of optimal timings for switching operations
of the rapier heads 1 and 2, which in turn facilitates setting of the
optimal timings for the gripping and releasing of the weft. On the other
hand, easiness in setting the optimal timings for gripping and releasing
of the weft can assure positive pick-up of the weft Y by the feeding
rapier head 1 as well as positive transfer of the weft Y from the feeding
rapier head 1 to the receiving rapier head 2.
In the case of the weft inserting apparatus according to the
instant embodiment of the invention, the spring member for gripping the
weft is rendered unnecessary. Further, the driving mechanism for shifting
the movable gripper 8C and 12C between the weft grip position and the weft
release position can be realized only by a small size piezoelectric
device, which contributes to further simplified and compact implementation
of the driving mechanisms mentioned previously. Incidentally, the
electric wires connected to the piezoelectric device may be replaced by
tapes or straps or tape-like material admixed with electrically conductive
material. Besides, the driving means may be implemented in the form of a
wireless driving means.
In the weft inserting apparatus according to the present
invention, permanent magnets can be used as the magnetic force exerting
means. By way of example, a permanent magnet may be disposed in the
vicinity of the retraction dead center position at the weft insertion
starting side. In the state in which the movable gripper of the feeding
rapier head for the weft transfer is disposed at the weft release
position, the weft insertion by the receiving rapier head is started. In
that case, the weft can positively be caught by the weft feeding rapier
head when such arrangement is adapted that the magnetic action of the
permanent magnet becomes rapidly lowered substantially at the time point
when the weft is caught. Alternatively, the permanent magnet may be
disposed in the vicinity of the retraction dead center position at the
weft insertion terminal side. The movable gripper of the receiving rapier
head is disposed at the weft release position under the action of the
magnetic force generated by the permanent magnet, whereupon the weft as
transported by the receiving rapier head is released therefrom.
As will now be understood from the foregoing description, with
such arrangement of the weft inserting apparatus for the rapier loom that
the movable gripper is positionally changed over between the weft grip
position and the weft release position by switching the magnetic force
exerting means between the state in which the magnetic force thereof acts
on the magnetic force responsive movable gripper and the state in which
the magnetic force does not act on the movable gripper or alternatively by
switching the piezoelectric stack means between the state in which a
voltage is applied thereto and the state in which no voltage is applied,
there is achieved the aimed advantageous effect that the weft insertion
can be performed with high reliability while substantially avoiding injury
or damage to the warps.
Many features and advantages of the present invention are apparent
form the detailed description and thus it is intended by the appended
claims to cover all such features and advantages of the system which fall
within the true spirit and scope of the invention. Further, since
numerous modifications and combinations will readily occur to those
skilled in the art, it is not intended to limit the invention to the exact
construction and operation illustrated and described.
By way of example, the present invention can be applied to a
rapier loom in which each of the rapier heads is secured at a tip end of a
rod which is adapted to be linearly and reciprocatively moved as well as a
rapier loom in which the weft insertion is performed only by using a
rapier head which is inserted into a shed defined by the warps from a weft
insertion starting side.
Accordingly, all suitable modifications and equivalents may be
resorted to, falling within the spirit and scope of the invention.
A weft inserting apparatus for a rapier loom for weaving a fabric
by inserting a weft through a shed formed by warps by reciprocatively
moving feeding and receiving rapier heads through the shed. The feeding
and receiving rapier heads (1; 2) are each constituted by a combination of
a stationary gripper member (7; 11) and a movable gripper member (8; 12)
made of a magnetic material. Electromagnets (18; 19) are disposed at both
ends of a sley (17), respectively, while electromagnets (20; 21) are
disposed at a mid portion of the sley. The movable gripper member (8) of
the feeding rapier head (1) positioned in opposition to the electromagnets
(19; 21) is displaced from a weft grip position to a weft release position
by controlling the magnetic action of the electromagnets (18; 20), while
the movable gripper member (12) of the receiving rapier head (2) disposed
oppositely to the electromagnets (19; 21) is displaced from the weft grip
position to the weft release position by controlling the magnetic action
of the electromagnets (19; 21). The weft insertion can be carried out
with high reliability while positively protecting the weft against injury.