BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a method for controlling use of compressed air in
a jet loom and a compressed-air supply/control apparatus for the jet loom.
2. Description of the Related Art
[0002] An apparatus for supplying compressed air to an air jet loom is disclosed in Japanese
Utility Model Application Publication No. 53582/1991 (JP-UA-3-53582) and Japanese
Unexamined Patent Application Publication No. 104962/1991 (JP-A-3-104962). In the
case of the apparatus disclosed in the first mentioned publication, a plurality of
air supply means having discharge pressures differing from one another and a plurality
of jet looms are interconnected by means of air pipes, wherein change-over valves
are installed in the air pipes for establishing selectively air supply paths between
the air supplying means and the jet looms. In other words, by selecting the air supply
path or passage by manipulating correspondingly the change-over valves, the air supplying
means having a desired discharge pressure can operatively be connected to the selected
jet loom(s) so that the air discharged at a desired pressure can be supplied to the
jet loom.
[0003] On the other hand, in the case of the apparatus disclosed in Japanese Unexamined
Patent Application Publication No. 104962/1991 (JP-A-3-104962), there is provided
a controller which is supplied with pressure information signals from pressure regulators
provided in association with a plurality of jet looms, respectively, together with
pressure information signals outputted from pressure sensors provided in association
with air tanks which are installed in compressed air Supplying passages. The controller
is so designed or programmed as to arithmetically determine two theoretical basic
pressure values differing from each other on the basis of maximum pressure values
obtained from the plurality of pressure regulators to thereby compare the detected
pressure values derived from the outputs of the pressure sensors with the two theoretical
basic pressure values. When the detected pressure value exceeds the theoretical basic
pressure of a greater value, the controller turns off the air compressor (i.e., stops
operation of the compressor), while the controller turns on (i.e., puts into operation)
the compressor, when the detected pressure is lower than the theoretical basic pressure
of smaller value. By virtue of such on/off control of the compressor, the compressed-air
supply pressure is so regulated as to fall within a range defined by the two theoretical
basic values.
[0004] As can readily be appreciated, when the pressure of the compressed air supplied to
the jet loom becomes lower than a desired pressure for some reason, there may arise
a problem that weft inserting operation can not be performed satisfactorily. In this
conjunction, it is to be mentioned that in the case of the conventional jet loom systems
such as mentioned above, there is neither disclosed nor suggested any measures for
coping with failure or fault in the weft inserting operation which may be brought
about when the compressed air supply pressure falls abnormally.
SUMMARY OF THE INVENTION
[0005] In the light of the state of the art described above, it is an object of the present
invention to provided a method controlling the use of compressed air in a jet loom
in dependence on a pressure at which the compressed air is supplied to the jet loom
from a compressed-air supply apparatus.
[0006] Another object of the invention is to provide an apparatus for carrying out the method
mentioned above.
[0007] In view of the above and other objects which will become apparent as the description
proceeds, it is proposed according to an aspect of the present invention that an air
supply pressure of compressed air supplied to a jet loom from a compressed-air supply
apparatus is detected and compared with a preset reference pressure, wherein use of
the compressed air in the jet loom is disabled when the detected air supply pressure
becomes lower than the preset reference pressure. Thus, when the detected air supply
pressure becomes lower than the preset pressure level, the weft inserting operation
effectuated by injecting or jetting the compressed air is stopped, whereby the weft
insertion can positively be protected against a failure or fault due to the pressure
lowering of the compressed air. Further, occurrence of abnormality in the jet loom
due to abnormal lowering of the compressed air supply pressure can positively be suppressed
or prevented.
[0008] According to another aspect of the invention, it is taught that an air supply pressure
of compressed air supplied to a jet loom from a compressed-air supply apparatus is
detected and then a period during which the detected air supply pressure is lower
than a preset reference pressure is detected to be subsequently compared with a preset
reference period, wherein use of the compressed air in the jet loom is disabled when
the detected period reaches or exceeds the reference period. Thus, faulty weft insertion
can positively be prevented.
[0009] In a preferred mode for carrying out the invention, operation of the jet loom may
be stopped substantially concurrently with the stoppage of the compressed air supply.
Thus, the stoppage of use of the compressed air in the jet loom is so interlocked
with stoppage of the loom operation that the weft inserting operation is inhibited
upon stoppage of the loom operation.
[0010] According to yet another aspect of the invention, it is proposed that a pressure
of compressed air supplied to a jet loom from a compressed-air supply apparatus is
detected to be subsequently compared with a preset reference pressure, wherein use
of the compressed air in the jet loom is enabled when the detected air supply pressure
is higher than the preset reference pressure. Thus, the weft inserting operation in
the jet loom is started only after the compressed air supply pressure exceeds the
preset pressure level, whereby occurrence of abnormality in the jet loom due to abnormal
lowering of the compressed air supply pressure can effectively be excluded.
[0011] In another preferred mode for carrying out the invention, such arrangement may be
adopted that the use of the compressed air in the jet loom is enabled substantially
concurrently with starting of operation of the jet loom.
[0012] According to a further aspect of the invention, there is provided a compressed-air
supply apparatus for a jet loom, which apparatus includes a compressor for producing
compressed air to be supplied to the jet loom, a pressure detecting means for detecting
an air supply pressure at which the compressed air is supplied to the jet loom from
the compressor through an air flow passage, a comparison means for comparing the air
supply pressure detected by the pressure detecting means with a preset reference pressure,
and a disabling decision means for issuing an inhibit signal for disabling the use
of the compressed air in the jet loom when the air supply pressure detected by the
pressure detecting means becomes lower than the preset reference pressure level. With
the arrangement of the compressed-air supply apparatus described above, the weft inserting
operation effected under the action of jet(s) of the compressed air is stopped when
the detected compressed air supply pressure becomes lower than the preset level, whereby
defective weft insertion due to the pressure lowering of the air jet(s) can effectively
be suppressed. Thus, the jet loom can be protected against abnormality which say otherwise
be brought about due to abnormal lowering of the compressed air supply pressure.
[0013] According to yet further aspect of the invention, there is provided a compressed-air
supply apparatus for a jet loom, which apparatus includes a compressor for producing
a compressed air to be supplied to the jet loom, a pressure detecting means for detecting
an air supply pressure at which the compressed air is supplied to the jet loom from
the compressor through an air flow passage, a period detecting means for detecting
a period during which the compressed air supply pressure detected by the pressure
detecting means remains lower than a preset reference pressure, a period comparing
means for comparing the period detected by the period detecting means with a preset
reference period, and a use disabling decision means for issuing an inhibit signal
for inhibiting use of the compressed air in the jet loom when it is detected as a
result of the period comparison that the period detected by the period detecting means
exceeds the preset reference period. Thus, when the period during which the detected
air supply pressure remains lower than the preset pressure level exceeds the preset
time period, weft inserting operation being effected under the action of the air jet(s)
is stopped, whereby the defective weft insertion can successfully be prevented.
[0014] In yet another preferred mode for carrying out the invention, the signal for inhibiting
use of the compressed air may serve additionally as a signal for stopping operation
of the jet loom.
[0015] Provided according to still further aspect of the invention is a compressed-air supply
apparatus for a jet loom, which apparatus includes a compressor for producing a compressed
air to be supplied to the jet loom, a pressure detecting means for detecting an air
supply pressure at which the compressed air is supplied to the jet loom from the compressor
through an air flow passage, a comparison means for comparing the air supply pressure
detected by the pressure detecting means with a preset reference pressure, and a use
enabling decision means for issuing an enable signal for enabling use of the compressed
air in the jet loom when the air supply pressure detected by the pressure detecting
means exceeds the preset reference pressure level. Thus, the weft inserting operation
in the jet loom is started only after the compressed air supply pressure exceeds the
preset pressure level, whereby occurrence of abnormality in the jet loom due to abnormal
lowering of the compressed air supply pressure can effectively be excluded.
[0016] In yet further preferred mode for carrying out the invention, the signal for enabling
the use of the compressed air may serve additionally as a signal for enabling operation
of the jet loom.
[0017] In a still further preferred mode for carrying out the invention, the use enabling
decision means may be so arranged as to decide whether the use enabling signal for
enabling the use of the compressed air is to be issued or not on the basis of the
information which is supplied from status signal transmitting means and which indicates
status of use of the compressed air in the jet loom.
[0018] With the above-mentioned arrangement of the compressed-air supply apparatus for the
jet loom, the status of use of the compressed air in the jet loom is transmitted or
informed to the use enabling decision means through the use status information signal
transmitting means. When the air is not used, the use enabling decision means enables
use of the compressed air only after the compressed air supply pressure exceeds the
preset pressure level. Thus, operation of the jet loom can be started with high security
and reliability.
[0019] 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
[0020] In the course of the description which follows, reference is made to the drawings,
in which:
Fig. 1 is a block diagram showing schematically compressed-air supply apparatuses
each provided in association with one jet loom according to a first embodiment of
the present invention;
Fig. 2 is a circuit diagram showing a configuration of a control circuit for the compressed-air
supply apparatus;
Fig. 3 is a timing chart for illustrating graphically variations in rotation speed
of an air compressor together with variation in pressure of compressed air discharged
from the same;
Fig. 4 is a timing chart for illustrating graphically variations in rotation speed
of the air compressor together with variations in the pressure of the compressed air
discharged from the same;
Fig. 5 is a circuit diagram showing an arrangement of a compressed-air supply apparatus
according to a second embodiment of the present invention;
Fig. 6 is a circuit diagram showing an arrangement of a control circuit employed in
the compressed-air supply apparatus according to the second embodiment of the invention;
Fig. 7 is a timing chart for illustrating graphically variations in rotation speed
of an air compressor together with variations in pressure supplied from the same in
the apparatus according to the second embodiment of the invention;
Fig. 8 is a block diagram showing a configuration of a control circuit employed in
a compressed-air supply apparatus according to a third embodiment of the present invention;
Fig. 9 is a circuit diagram showing a configuration of a control circuit for the compressed-air
supply apparatus according to the third embodiment of the invention; and
Fig. 10 is a timing chart for illustrating graphically variations in rotation speed
of an air compressor together with variations in pressure discharged from the same
in the apparatus according to the third embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] 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.
Embodiment 1
[0022] Now, referring to Figs. 1 to 4, description will be made of a first referred mode
for carrying out the invention, i.e., a first exemplary embodiment thereof.
[0023] Fig. 1 is a block diagram showing schematically a compressed-air supply control system
for e.g., two jet looms provided for parallel operations independent of each other.
That is, the compressed air supply control system comprises two subsystems each operatively
associated with the corresponding air jet looms. Referring to Fig. 1, each of the
air jet looms (hereinafter referred to simply as the jet loom in abbreviation) generally
designated by a reference numeral 1 is provided with a loom driving motor 2 which
is under the control of a loom control computer C
0 serving also as a speed control command means. The loom control computer C
0 responds to a turning-on or closing operation of a starting switch 3 constituting
a starting means, to thereby perform an operation control of the loom driving motor
2 and energization/deenergization controls of solenoid-operated on/off valve devices
4A and 4B. In the jet loom 1, a weft is inserted into an inter-warp opening under
the action of air jet injected by a weft inserting main nozzle (not shown), wherein
the weft inserted into the inter-warp opening is caused to run therethrough under
the action of air jets injected successively and sequentially in a relay-like fashion
by means of a plurality of auxiliary nozzles (not shown ). In Fig. 1, reference character
4A designates a solenoid-operated on/off valve device (also referred to as an electromagnetic
change-over valve device) which serves for controlling the supply of compressed air
to the weft inserting main nozzle (i.e., changing over the air supplying state and
the air-supply stopped state for the weft inserting main nozzle) while reference character
4B designates a solenoid-operated on/off valve for controlling the supply of the compressed
air to the weft inserting auxiliary nozzles. The weft inserting main nozzle (not shown)
is connected in series to the solenoid-operated on/off valve device 4A, a main compressed-air
tank 20A and a pressure regulator 13A. Similarly, the weft inserting auxiliary nozzles
(not shown ) are connected in series to the solenoid-operated on/off valve device
4B, an auxiliary compressed-air tank 20B and a pressure regulator 13B.
[0024] A reference numeral 5 generally designates a compressed-air supply/control apparatus
which is destined to be employed in association with the jet loom 1 on a one-by-one
basis. The compressed-air supply/control apparatus 5 is comprised of a discharge flow
rate determining circuit 6, an inverter 7 constituting a part of a discharge flow
rate change-over means, a pulse motor 8 also constituting a part of the discharge
flow rate change-over means, an air compressor 9 of a fixed capacity type, a pressure-responsive
on/off switch 10 which is employed as a pressure detecting means and a disabling decision
circuit 14. The pressure-responsive on/off switch 10 is so arranged as to detect the
pressure within a compressed air supplying passage 11 which extends from the air compressor
9 of the fixed capacity type to the jet loom 1. As can be seen from Fig. 3, when the
pressure within the compressed air supplying passage 11 becomes equal to or exceeds
a first reference pressure P
1, the pressure-responsive on/off switch 10 is turned off. This state (i.e., off-state)
is held until the pressure within the compressed air supplying passage 11 has reduced
to a second reference pressure P
2 (< P
1). When the pressure of the compressed air supplying passage 11 becomes equal to or
lower than the second reference pressure P
2, the pressure-responsive on/off switch 10 is then turned on. This on-state of the
switch 10 is held until the pressure of the compressed air supplying passage 11 has
increased up to the first reference pressure P
1.
[0025] Fig. 2 shows an electric control circuit for the compressed-air supply/control apparatus
5. The inverter 7 which serves as a frequency converter outputs to the pulse motor
8 an electric power of a pulse frequency resulting from a frequency conversion of
the output power of a three-phase AC power source 12. The pulse motor 8 (which may
also be referred to as the variable-speed motor) is designed to rotate at a rotation
speed (rpm) which is in proportion to the pulse frequency of the electric power supplied
from the inverter 7, while the air compressor 9 of fixed capacity type operates to
discharge an amount of compressed air which depends on the rotation speed of the pulse
motor 8. Consequently, the discharged air flow rate in the compressed air supplying
passage 11 per unit time increases as the rotation speed of the pulse motor 8 increases.
[0026] A status information transmitting switch 3A constituting a part of the discharge
flow rate determining circuit 6 (see Fig. 2) is adapted to operate in response to
on/off commands issued from the loom control computer C
0. More specifically, the loom control computer C
0 closes or turns on the status information transmitting switch 3A in response to the
turn-on operation of the starting switch 3. On the other hand, when an operation stop
signal S (see Fig. 3) is inputted to the loom control computer C
0, the status information transmitting switch 3A is tuned off by the loom control computer
C
0.
[0027] The air-use disabling decision circuit 14 (see Fig. 2) is comprised of an normally
opened contact OP
14 and a period detecting circuit 15. When a closed state of the normally opened contact
OP
14 continues for a period longer than a preset period T
1 from a time point when the normally opened contact OP
14 is changed over to the closed state from the open state, the period detecting circuit
15 outputs the operation stop signal S to the loom control computer C
0.
[0028] The inverter 7 is provided with a common terminal 7a together with a predetermined
number (three in the illustrated apparatus) of converted-frequency selecting terminals
7b, 7c and 7d. A curve E
1 illustrated in Fig. 3 represents graphically the rotation speed of the air compressor
9 of the fixed capacity type. Further, a curve E
2 illustrated in Fig. 3 represents graphically change-over of an electrical connection
with an electrical disconnection between the terminals 7a and 7b. As can be seen,
when both a normally closed contact CL
11 and a normally opened contact OP
21 shown in Fig. 2 are closed concurrently, the terminals 7a and 7b are electrically
connected. A curve E
3 in Fig. 3 represents graphically change-over of an electrical connection with an
electrical disconnection between the terminals 7a and 7c. As can be seen, when both
a normally opened contact OP
12 and a normally closed contact CL
22 shown in Fig. 2 are closed concurrently, the terminals 7a and 7c are electrically
connected. Furthermore, a curve E
4 in Fig. 3 represents graphically change-over of an electrical connection with an
electrical disconnection between the terminals 7a and 7d. When one of normally opened
contacts OP
13 and OP
23 connected in parallel is closed, there is formed an electric connection between the
terminals 7a and 7d.
[0029] When the electric connection is formed neither between the terminals 7a and 7b, the
terminals 7a and 7c nor between the terminals 7a and 7d, the inverter 7 outputs no
electric power. In the state where the terminals 7a and 7b are disconnected while
the electric connections are formed between the terminals 7a and 7c and between the
terminals 7a and 7d, respectively, the inverter 7 outputs the electric power of a
converted frequency which is effective to set the rotation speed of the inverter 7
to a speed N
3 (rpm). On the other hand, when the terminals 7a and 7b on one hand and the terminals
7a and 7d on the other hand are electrically connected, respectively, with the terminals
7a and 7c being electrically disconnected, the inverter outputs the electric power
of a converted pulse frequency which sets the rotation speed of the air compressor
9 to a second rotation speed N
2 (> N
3). Furthermore, in the state where electrical disconnection exists between the terminals
7a and 7b and between the terminals 7a and 7c with the terminals 7a and 7d being electrically
connected to each other, the inverter 7 outputs the electric power of a converted
pulse frequency for setting the rotation speed of the air compressor 9 to the first
rotation speed N
1 (> N
2).
[0030] Further referring to Fig. 3, a curve E
5 represents the on/off state of the status information transmitting switch 3A (see
Fig. 2). In this conjunction, it should be mentioned that the on-off state of the
status information transmitting switch 3A corresponds to that of the starting switch
3. Further, a curve E
6 shown in Fig. 3 represents the on/off state of the pressure-responsive on/off switch
10, while a curve E
7 represents variation of the pressure within the compressed air supplying passage
11. When the jet loom 1 is in the shutdown state (i.e., stopped) with the air compressor
9 being in the non-operative state, the pressure within the compressed air supplying
passage 11 assumes a low level near to the atmospheric pressure. In that case, the
pressure-responsive on/off switch 10 assumes the closed state (i.e., the on-state).
The three-phase AC power source 12 is turned on at a time point t
0. When the three-phase AC power source 12 is turned on, then the relay CR
1 is electrically energized, whereby the normally closed contact CL
11 is opened while the normally opened contacts OP
12 and OP
13 are closed (i.e., turned on). In this state, the terminals 7a and 7b are electrically
disconnected from each other, while electrical connections are formed between the
terminals 7a and 7c and between the terminals 7a and 7d, respectively. Thus, when
the three-phase AC power source 12 is turned on, the air compressor 9 starts to rotate
at the rotation speed N
3, which results in that the compressed air is supplied to the jet loom 1 by way of
the compressed air supplying passage 11.
[0031] A straight line E
8 indicates that the operation stop signal S is not outputted from the period detecting
circuit 15.
[0032] When the pressure within the compressed air supplying passage 11 exceeds the first
reference pressure P
1, the pressure-responsive on/off switch 10 is turned off (i.e., opened state), causing
the relay CR
1 to be electrically deenergized. Upon deenergization of the relay CR
1, the normally closed contact CL
11 is closed with the normally opened contacts OP
12 and OP
13 being opened. In this state, there prevails electrically disconnected states between
the terminals 7a and 7b, between the terminals 7a and 7c and between the terminals
7a and 7d, respectively. Thus, the inverter 7 stops outputting the pulse frequency
electric power, to thereby stop the operation of the compressor 9. As can be seen
in Fig. 1, the compressed air within the compressed air supplying passage 11 is supplied
to the weft inserting main nozzle by way of the pressure regulator 13. At this junction,
it should be mentioned that the pressure regulator 13 is set at a considerably lower
pressure P
0 than the second reference pressure P
2. To say in another way, the pressure of the compressed air which is higher than the
pressure P
0 is lowered to the pressure P
0, whereupon the compressed air is supplied to the weft inserting main nozzle. Thus,
the air as supplied is jetted from the weft inserting main nozzle at the pressure
P
0. Because the pressure P
0 is low, the posture of the tip end portion of the weft in the standby state is rectified
into a linear form under the action of the air jet, which contributes to suppression
of occurrence of error or fault in the weft insertion.
[0033] When the operation of the air compressor 9 is stopped, the pressure within the compressed
air supplying passage 11 decreases. In that case, when the pressure within the compressed
air supplying passage 11 becomes lower than the second reference pressure P
2, the pressure-responsive on/off switch 10 is turned on, to thereby start rotation
of the air compressor 9 at the rotation speed N
3. Thus, when the status information transmitting switch 3A is in the off-state, i.e.,
when the starting switch 3 is opened (OFF) to say in another way, the pressure within
the compressed air supplying passage 11 is regulated to a level intermediate between
the first reference pressure P
1 and the second reference pressure P
2.
[0034] At a time point t
1, the status information transmitting switch 3A is closed or turned on. In the case
as illustrated, the pressure within the compressed air supplying passage 11 at the
time point t
1 is reduced with no electric connections being formed between the terminals 7a and
7b, between terminals 7a and 7c and between the terminals 7a and 7d. Consequently,
the air compressor 9 is in the inoperative state. When the status information transmitting
switch 3A is closed (turned on), the relay CR
2 is electrically energized to close the normally opened contacts OP
21 and OP
23 while opening the normally closed contact CL
22. In this state, electrical connections are formed between the terminals 7a and 7b
and between the terminals 7a and 7d, respectively, while the terminals 7a and 7c are
electrically disconnected from each other. Thus, when the starting switch 3 is closed
in the state where the pressure within the compressed air supplying passage 11 is
low, the air compressor 9 is rotated at the second rotation speed N
2.
[0035] In response to the closing of the starting switch 3, the loom control computer C
0 activates the loom driving motor 2 while performing electric energization/deenergization
of the solenoid-operated on/off valve devices 4A and 4B. In synchronism with the energization/deenergization
of the solenoid-operated on/off valve devices 4A and 4B, the weft inserting main nozzle
and the weft inserting auxiliary nozzles produce air jets at predetermined rotation
angular positions, respectively, during every rotation of the jet loom 1. Under the
actions of these air jets, insertion of the weft is carried out. The consumption of
the compressed air used in the jet loom for the weft inserting air injections will
exceed an amount of the compressed air supplied from the air compressor 9 operating
at the second rotation speed N
2, which involves gradual lowering of the pressure within the compressed air supplying
passage 11. In that case, when the pressure within the compressed air supplying passage
11 becomes lower than the second reference pressure P
2, the relay CR
1 is electrically energized. When both the relays CR
1 and CR
2 are in the electrically energized state, the normally closed contacts CL
11 and CL
22 are opened while the normally opened contacts OP
12, OP
13, OP
21 and OP
23 are closed. In this state, the electrical conductions between the terminals 7a and
7b and between the terminals 7a and 7c are broken while electrically conducting state
is established between the terminals 7a and 7d. Thus, the air compressor 9 is caused
to rotate at the first rotation speed N
1. In this conjunction, it should be noted that the consumption of the compressed air
as brought about by injection of the air jets from the weft inserting main nozzle
and the weft inserting auxiliary nozzles is smaller than the amount of compressed
air supplied from the air compressor 9 operating at the first rotation speed N
1. As a consequence, the pressure within the compressed air supplying passage 11 rises
progressively.
[0036] When the pressure within the compressed air supplying passage 11 rises beyond the
first reference pressure P
1, the relay CR
1 is electrically deenergized. Thus, the state in which both the relays CR
1 and CR
2 are electrically energized is changed over to the state where the relay CR
1 is deenergized with the relay CR
2 being energized, whereby the rotation speed of the air compressor 9 decreases from
the first rotation speed N
1 to the second rotation speed N
2. Owing to such lowering of the rotation speed, the pressure within the compressed
air supplying passage 11 decreases gradually from the first reference pressure P
1 toward the second reference pressure P
2. Thus, it is safe to say that the pressure within the compressed air supplying passage
11 in the state in which the starting switch 3 is closed is regulated to a level intermediate
between the first reference pressure P
1 and the second reference pressure P
2.
[0037] The discharge flow rate determining circuit 6 serves to control the rotation speed
of the pulse motor 8 selectively at four speed stages or levels in dependence on the
on/off states of the status information transmitting switch 3A which constitutes an
operation status transmit means for transmitting or informing the pressure detection
state of the pressure-responsive on/off switch 10 and the operation status of the
jet loom 1. More specifically, when the starting switch 3 is in the off-state, the
discharge flow rate determining circuit 6 determines either a discharge flow rate
regulating mode in which the rotation speed of the air compressor 9 is set to zero
or a discharge flow rate regulating mode in which the rotation speed of the air compressor
9 is set to the rotation speed N
3 on the basis of the result of comparison between the two reference pressures P
1 and P
2 and the detected pressure. By contrast, when the starting switch 3 is in the on-state,
the discharge flow rate determining circuit 6 determines either a first discharge
flow rate regulating mode in which the rotation speed of theair compressor 9 is set
to the second rotation speed N
2 or alternatively a second discharge flow rate regulating mode in which the rotation
speed of the air compressor 9 is set to the first rotation speed N
1 on the basis of the result of comparison between the two reference pressures P
1 and P
2 and the detected pressure.
[0038] In the state where the starting switch 3 is in the on-state, a great amount of the
compressed air will be consumed by the jet loom 1. Accordingly, with the control of
the compressed air supply by turning on/off the compressor in the state where the
consumption of the compressed air is of a large amount, a steep lowering of the pressure
under which the compressed air is supplied to the jet loom 1 can not be avoided. It
will readily be understood that such steep lowering of the compressed air supply pressure
is likely to bring about a fault or failure in the weft insertion. In this conjunction,
it should be noted that by selecting appropriately or properly the two rotation speeds
N
1 and N
2 of the air compressor 9, as taught by the invention, the difference or gap between
the reference pressures P
1 and P
2 can be decreased, whereby the range defined by the reference pressures P
1 and P
2 can be regulated to such a range in which variation in the weft inserting air injection
pressure can provide no obstacle to a satisfactory weft insertion. Besides, variation
in the pressure within the compressed air supplying passage 11 is limited to the range
defined between the reference pressures P
1 and P
2, whereby steep lowering of the compressed air supply pressure can positively be suppressed.
[0039] In general, the reference pressures P
1 and P
2 are determined in consideration of the types of the weft, the rotation speed of the
jet loom and others. It is however desirable to alter or update the rotation speed
of the air compressor 9 when the reference pressures P
1 and P
2 are changed. In this conjunction, it should be appreciated that the use of the pulse
motor 8 serving as a variable speed driving motor in combination with the inverter
7 constituting the discharge flow rate change-over means makes it easy to set selectively
the rotation speed of the air compressor 9.
[0040] At this juncture, it is noted that there may arise such unwanted situation that the
state in which the air supply pressure lower than the second reference pressure P
2 continues to exist due to occurrence of abnormality in the compressor, pressure leakage
and/or for some other reasons. In that case, the weft inserting operation cannot be
carried out satisfactorily with the leading end of the weft reaching short of a predetermined
destination or terminal position. Parenthetically, there is installed at the predetermined
terminal position a weft detector for detecting arrival of the leading end of the
weft. Thus, when the leading end of the weft does not arrive at the predetermined
terminal position, the weft detector generates an operation stop signal to the loom
control computer C
0. Additionally, such a problem may arise that the quality of woven fabric is degraded
due to unfavorable or unsatisfactory posture or positioning of the weft even when
the leading end of the weft can reach the predetermined terminal position.
[0041] Incidentally, a curve E
71 shown in Fig. 4 represents, by way of example only, a manner in which the compressed
air supply pressure becomes lower without attaining the first reference pressure P
1 in the course of operation of the jet loom 1. In the case of this example, it is
assumed that such a pressure leakage takes place that the compressed air supply pressure
lowers below the second reference pressure P
2 without rising up to the first reference pressure P
1 after closing of the pressure-responsive on/off switch 10 at a time point t
2. More specifically, when the pressure-responsive on/off switch 10 is closed (i.e.,
turned on), the relay CR
1 is electrically energized, whereby the normally opened contact OP
14 is closed. When the on-state (closed state) of the normally opened contact OP
14 is changed over to the off-state (opened state) within the preset period T
1, the period detecting circuit 15 does not output the operation stop signal S. On
the contrary, when the state in which the normally opened contact OP
14 continues to be in the on-state (closed state) over a time span longer than the preset
period T
1, the period detecting circuit 15 outputs the operation stop signal S. A curve E
81 shown in Fig. 4 indicates presence and absence of the operation stop signal S outputted
from the period detecting circuit 15. Parenthetically, curves E
11, E
21, E
31, E
41, E
51 and E
61 correspond to the curves E
1, E
2, E
3, E
4, E
5 and E
6, respectively. In the case of the example illustrated in Fig. 4, the pressure-responsive
on/off switch 10 is not turned off until the preset period T
1 has lapsed from the time point t
2 at which the pressure-responsive on/off switch 10 was closed. Consequently, the closed
state (on-state) of the normally opened contact OP
14 continues to exist beyond the preset period T
1. Consequently, the period detecting circuit 15 issues the operation stop signal S
to the loom control computer C
0 at a time point t
3 after lapse of the preset period T
1 from the time point t
2.
[0042] In response to the inputting of the operation stop signal S, the loom control computer
C
0 issues a command for stopping operation of the loom driving motor 2 as well as a
command for electrically deenergizing the solenoid-operated on/off valve device 4,
while turning off the status information transmitting switch 3A. As a consequence,
the relay CR
2 is electrically deenergized, whereby the normally closed contact CL
22 is closed while the normally opened contacts OP
21 and OP
23 are opened, to thereby cause the pulse motor 8 to rotate at the rotation speed N
3 after the time point t
3. Additionally, air jets through the weft inserting main nozzle and a weft inserting
auxiliary nozzle are interrupted with the operation of the jet loom 1 being stopped
substantially concurrently. In this way, the use of the compressed air in the jet
loom can be controlled properly such that the weft inserting air jets are interrupted
upon occurrence of abnormal lowering of the compressed air supply pressure, whereby
occurrence of error in the weft insertion or quality degradation of the woven fabric
can be suppressed to a possible minimum.
[0043] As is apparent from the foregoing description, in the case of the compressed-air
supply/control apparatus according to the instant embodiment of the invention, the
pressure-responsive on/off switch 10 for maintaining the compressed air pressure at
an appropriate level within the pressure range of P
1 to P
2 is utilized for controlling properly the use or consumption status of the compressed
air in the jet loom 1. It should be mentioned that the arrangement which allows the
pressure-responsive on/off switch 10 to be used additionally for the control for establishing
the effective utilization of the compressed air is advantageous in response to reduction
of the total cost involved in implementing the compressed-air supply/control apparatus
even when the pressure-responsive on/off switch 10 itself is expensive. Besides, when
compared with the arrangement in which a plurality of pressure detectors are used,
employment of a single pressure detector contributes to significant simplification
of the piping arrangement of the compressed air supplying passage 11 in the compressed
air supplying system.
Embodiment 2
[0044] Next, referring to Figs. 5 to 7, a second embodiment of the present invention will
be described. In these figures, components similar or equivalent to those of the apparatus
according to the first embodiment described above are designated by like reference
characters. Thus, repeated description of these components will be unnecessary. In
the compressed-air supply/control apparatus generally denoted by reference character
5A according to the instant embodiment of the invention, the compressed air pressure
within the compressed air supplying passage 11 is detected by a pressure-responsive
on/off switch 16. More specifically, when the detected air supply pressure exceeds
a preset pressure P
3, the pressure-responsive on/off switch 16 is closed (i.e., turned on). In the case
of the instant embodiment of the invention, the preset pressure P
3 is set slightly lower than the second reference pressure P
2. An operation enabling decision circuit 17 responds to the on-state of the pressure-responsive
on/off switch 16 to generate an operation enabling signal H. A curve E
9 shown in Fig. 7 illustrates presence/absence of the output of the operation enabling
signal H. So long as the operation enabling signal H is inputted, the loom control
computer C
0 assumes the state in which the on-signal from the starting switch 3 is validated.
When the starting switch 3 in the standby state is closed or turned on, the loom control
signal C
0 commands activation of the loom driving motor 2 as well as the electrical energization/deenergization
of the solenoid-operated on/off valve devices 4A and 4B.
[0045] Unless the compressed air supply pressure reaches the preset pressure P
3, the pressure-responsive on/off switch 16 does not output the on-signal to the operation
enabling decision circuit 17. As a consequence, the operation enabling signal H is
not outputted to the loom control signal C
0 from the decision circuit 17. Thus, so long as the compressed air supply pressure
does not reach the preset pressure P
3 due to occurrence of abnormality in the air compressor, pressure leakage or for some
other reasons, the weft inserting operation can not be started. The preset pressure
P
3 is so set as to be only slightly lower than the second reference pressure P
2. The air jet pressure for the weft insertion may be regarded as a suitable injection
pressure when compressed air supply pressure is the preset pressure P
3. Additionally, because of the proper control of the use status of the compressed
air in the jet loom such that the weft inserting air injection is inhibited or disabled
when the compressed air supply pressure is insufficient, occurrence of failure or
fault in the weft insertion due to abnormal compressed air supply pressure can be
suppressed to a minimum.
Embodiment 3
[0046] Figs. 8 to 10 are views for illustrating the compressed-air supply/control apparatus
for a jet loom according to a third embodiment of the present Invention. In these
figures, components or parts same as or equivalent to those of the compressed-air
supply/control apparatus according to the second embodiment are designated by like
reference characters. Accordingly, repeated description thereof is omitted. In the
compressed-air supply/control apparatus 5B according to the instant embodiment of
the invention, a pair of change-over detecting circuits 18 and 19 are provided for
outputting change-over detection signals F generated in response to the on-and-off
operations of the pressure-responsive on/off switch 10, respectively, to the operation
disabling decision circuit 20. The change-over detecting circuit 18 is comprised of
a normally opened contact OP
15 and a pulse signal output circuit 21. On the other hand, the change-over detecting
circuit 19 is comprised of the normally closed contact CL
15 and a pulse signal output circuit 22. Every time the normally opened contact OP
15 is changed over from the opened state to the closed state, the pulse signal output
circuit 21 outputs the pulse-like change-over detection signal F, while the pulse
signal output circuit 22 outputs the pulse-like change-over detection signal every
time the normally closed contact CL
15 is changed over from the opened state (off-state) to the closed state (on-state).
A curve E
10 shown in Fig. 10 illustrates the presence/absence of the change-over detection signal
F.
[0047] When the interval at which the change-over detection signal F is inputted attains
or exceeds the preset period T
2, the disabling decision circuit 20 outputs the operation stop signal S to the loom
control computer C
0. Of course, unless the input interval of the change-over detection signal F reaches
the preset period T
2, the disabling decision circuit 20 does not issue the operation stop signal S. It
is to be mentioned that the preset period T
2 is set longer than the interval at which the pressure-responsive on/off switch 10
is turned on and off in the normal operation of the jet loom 1. As can be seen from
a curve E
72 shown in Fig. 10, when the interval at which the pressure-responsive on/off switch
10 is turned on and off due to abnormal lowering of the compressed air supply pressure
attains the preset period T
2, the operation disabling decision circuit 20 outputs the operation stop signal S.
In this manner, suitable control of the use or consumption status of the compressed
air in the jet loom can be carried out with the weft inserting air injection being
disabled when the compressed air pressure is insufficient, whereby undesirable possibility
of occurrence error in the weft insertion can positively be suppressed to a minimum.
[0048] The teachings of the present invention can be applied to operation control of the
weft processing apparatus such as disclosed in Japanese Unexamined Patent Application
Publication No. 90755/1995 (JP-A-7-90755). In this type of the weft inserting apparatus,
even when error should occur in the insertion of a weft, a succeeding weft can be
discharged from the weft inserting main nozzle without need for separating or cutting
off the succeeding weft from the preceding one suffering error, whereupon the succeeding
weft as injected is prevented from traveling through the inter-warp path and displaced
to a weft withdrawing route from the weft inserting path. Subsequently, the weft inserted
erroneously is withdrawn from the cloth fell to be eliminated by finding the trace
of the succeeding weft which is prevented from insertion. Prevention of insertion
of the succeeding weft is effectuated by an air flow in the direction orthogonal to
that of the weft inserting air flow passage, wherein a suction air flow is utilized
for withdrawing the weft undergone the erroneous insertion. Thus, when the pressure
of the compressed air used in the weft processing apparatus of the type mentioned
above lowers abnormally, the weft undergone the erroneous insertion can positively
be removed from the cloth fell of a woven fabric. When the compressed air supply pressure
falls abnormally, operation of the weft processing apparatus may be inhibited or may
be enabled in dependence on the results of the compressed air supply pressure as detected.
In that case, the signal outputted from the use disabling decision circuit 14, 20
represents a signal for inhibiting use or consumption of the compressed air in the
jet loom while the signal outputted from the use enabling decision circuit 17 may
be used for allowing the operation of the jet loom to start.
[0049] Many features and advantages of the present invention are apparent from 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.
[0050] By way of example, it is also possible to supply or feed the compressed air from
a single compressed-air supply/control apparatus to a plurality of jet looms weaving
a same kind of cloth. Accordingly, all suitable modifications and equivalents may
be resorted to, falling within the spirit and scope of the invention.
[0051] Method and apparatus for properly controlling a status of use of compressed air in
a jet loom. A compressed-air supply/control apparatus (5) includes a discharge flow
rate determining circuit (6), an inverter (7) constituting a part of a discharge flow
rate change-over means, a pulse motor (8) constituting another part of the discharge
flow rate change-over means, an air compressor (9) of fixed capacity type, a pressure-responsive
on/off switch (10) employed as a pressure detecting means and operation enable/disable
decision circuit (14). The pressure-responsive on/off switch (10) serves to detect
a pressure within a compressed air supplying passage (11) which extends from the air
compressor (9) to the jet loom (1). The operation enable/disable decision circuit
responds to an output of a period detecting circuit (15) to thereby issue an operation
stop signal (S) to the loom control computer C0 when an on-state of the pressure-responsive
on/off switch (10) continues for a period longer than a preset one.