Field of the invention
[0001] The present invention relates to a modulated drive weaving loom and to a weaving
controlling method employing said loom.
Background art
[0002] As is known, conventionally the drive system of a weaving loom comprises at least
one main motor able to actuate a main shaft by means of a suitable friction clutch
and a flywheel. The main shaft, in addition to transmitting motion to the main components,
such as the sley and - in gripper looms - the actual grippers, drives also to secondary
shafts which control other components, for example the weaving machine. Moreover,
one or more auxiliary motors may be envisaged for operation of the loom at a slow
speed or in reverse.
[0003] In the past, efforts have always been directed towards ensuring as uniform as possible
operating speed of the loom, despite the fact that the inertia forces and resistance
torques vary a number of times within the same operating cycle of the loom. For this
purpose, a flywheel was used, said flywheel representing an effective mechanical system
able to absorb a momentum, during the phases when the resistance torque decreases,
and restore said momentum during the phases when the resistance torque increases,
thereby avoiding an excessive loss of power (in particular during acceleration peaks)
and a certain uniformity of operation. With this system, moreover, it was possible
to use drive systems with a limited power - and therefore cost - whilst still achieving
a uniform power consumption and speed of rotation of the main shaft.
[0004] Owing to the uniform rotation of the main shaft, it was possible to set in a accurate
and repeatable manner the motion law of the individual components (for example, sley,
dobby, grippers, etc.) by means of suitable kinematic chains, such as crank systems
and cams. An important example of these kinematic mechanisms is represented by the
well-known variable-pitch screw cam system for actuating the gripper, for example
as also described in EP 164,627.
[0005] Recently weaving looms equipped with direct-drive systems have appeared, in other
words systems where a flywheel for regulating the speed during the operating cycle
is no longer used. An example of this loom is described in EP-A-1,158,081.
[0006] Said weaving looms equipped with direct-drive systems allow the weaving program to
be set according to the physical characteristics of the yarn and the surrounding conditions
in which the said looms are operating.
[0007] It has been found, moreover, that there are some circumstances for which it is desirable
to find solutions more advantageous than those offered by the known art.
[0008] One of these weaving-related requirements, which arises upon weaving various yarns
with an air jet loom, is that of keeping the behaviour of the weft as constant as
possible (repeatability) during insertion, despite the variability in the physical
characteristics and load conditions which occur between the start and end of the weft
yarn reel. At present it is possible to take into account this variability to a very
limited degree, for example by means of "air control" systems used in the air jet
looms, said systems controlling the stresses imparted to the weft yarn by regulating
the flowrate of the air output by the nozzle.
[0009] Further, there are many other factors which vary with the characteristics of the
yarn. For example, some yarns are very sensitive to the friction against the grippers,
therefore it is required to set a long shed opening time in order to allow insertion
of the weft without difficulty, something which inevitably slows down the average
speed of the loom; in other cases a greater amount of friction may be tolerated, thus
allowing to increase the weaving speed.
[0010] A further requirement occurs in natural, synthetic or artificial flock yarns which
have a relatively low strength and therefore in any case result in the need for a
sufficiently low insertion speed of the weft yarn and consequently low speed of the
entire loom.
[0011] All these individual requirements are met in the looms of the prior art using specific
groups of cams or kinematic mechanisms associated with the weaving components which
must be varied depending on the specific articles, regulating the kinematic mechanisms
or cam components so that the motion laws are redefined in such a way as to have efficient
operation in the new conditions. This, as can be understood, is somewhat complex.
[0012] For example, in the case of an air jet loom, it is desirable to be able to adapt
operation of the loom to the weft insertion timing (duration of insertion and time
of arrival) which can be in turn be determined on the basis of the yarn. The problems
which arise from an incorrect weft arrival time and other problems associated with
a "slack weft" and "inset weft" are currently solved by reducing the speed of the
loom or by changing - mechanically (i.e. with replacement of the sley cams) - the
time available for insertion.
[0013] The Applicant has instead decided to abandon the usual approach, investigating totally
new areas and leaving aside the established findings and theories which existed hitherto
in this field, in order to be able to obtain a loom which overcomes at least partially
the drawbacks of the prior art.
Summary of the invention
[0014] The object of the present invention, therefore, is that of obtaining the maximum
benefit from the direct-drive system by providing a direct-drive loom which is controlled
in an efficient manner so as to obtain the best result in weaving terms. This result
is achieved by departing in an original manner from the traditional approach of attempting
to achieve continuity and uniformity of operation and instead searching in an original
and inventive manner the best possible way of exploiting the new capabilities and
flexibility offered by a direct-drive loom.
[0015] According to the invention a new technology for controlling the motor is implemented,
said technology exploiting the possibility of varying, within a cycle or over several
cycles, the speed of the said motor - and therefore at least the main shaft of the
loom - so to vary correspondingly the motion law of the main weaving components (sley,
grippers, heald frames) associated therewith.
[0016] A preferred embodiment provides that the variation in speed is advantageously managed
so as to increase the duration of the insertion period of the weft yarn (a phase which
is undoubtedly critical for the quality of the final fabric) as needed and correspondingly
shorten a portion of the working cycle which is less critical (for example beating-up)
in order to recover "lost" time.
[0017] According to a first aspect, therefore, a direct-drive loom is provided where the
speed of rotation of the single motor is varied within one or more cycles.
[0018] According to a further aspect, the speed of the motor is varied within the cycle
on the basis of the requirements of a main weaving component, the motion law of the
other components being determined on the basis of the former. In this way, for example,
it is possible to define the speed law curve of the motor so as to obtain the desired
motion law of the grippers using a mechanism which is simplified and cheap (for example,
in the case of the screw mechanism a system with a constant pitch, instead of a variable
pitch may be used). The average operating speed of the loom is nevertheless constant.
[0019] According to another aspect of the invention, the motor speed is varied so as to
satisfy "on average" the overall operating requirement of the loom, optimising the
general behaviour thereof; for example, as already mentioned, by obtaining a reduction
in speed during the part of the cycle where insertion is performed, so that a greater
amount of time is available with the sley in the backward position and correspondingly
a greater amount of time is available with the shed open. This situation is particularly
convenient for those articles woven using an air jet loom (for example synthetic yarns)
for which the phase of crossing-over of the yarns coincides with or is slightly different
from beating-up time of the loom.
[0020] According to yet another aspect, the motion law of the motor is gradually varied
from one cycle to another, for example in order to take into account the variations
in the unwinding characteristics of the weft yarn between the fill and empty reel;
in particular, the period of time during which the shed is kept open for insertion
of the weft is gradually reduced upon reduction of the yarn still stored in the reel.
[0021] According to another aspect, a dual-drive loom is provided, i.e. with one drive for
the main components and another drive for the weaving machine - in which an independent
variation in the speed of the two main motors of the loom is established so as to
regulate and vary independently the motion law of the loom and the weaving machine
and reduce further the need for replacement of the mechanical control components (for
example, cams and kinematic mechanisms) in order to achieve a greater operating flexibility
and efficiency.
[0022] According to another aspect, the invention provides a method for controlling weaving
of a loom in which the instant of arrival of the weft yarn is detected by means of
suitable sensors (for example, photocells, etc.), establishing the statistical progression
of the weft arrival over time and modifying the speed, within a cycle, of at least
the main motor (if necessary also of the weaving machine) in order to alter the duration
of the time available for insertion on the basis of said establishment. Combined operation
with the air control device, which is designed to launch the weft yarn in air jet
looms, are also preferably envisaged.
[0023] Yet another aspect of the invention relates to a method which envisages determining
the motion law of the main motor on the basis of strength parameters of the weft yarns
so as to establish - for each single weft (in the case of an article which envisages
the insertion of several wefts with different strength characteristics) - the proper
and sufficient time for insertion of the said weft, with the correct air flowrate
so that the yarn does not break, correspondingly increasing or reducing in an optimum
manner the time available for insertion. Advantageously, by means of statistical processing
of the number of weft breakages, it is possible to modify the calculation of the speed
profile of the loom as a function of the different wefts, without stopping operation,
keeping always below the maximum limit the stresses which act on the individual weft
(adjustable for example by means of the air flow parameters of the air jet device)
within the specific operating conditions.
Brief description of the drawings
[0024] Further characteristic features and advantages of the loom and the associated control
method according to the invention will nevertheless emerge more clearly from the detailed
description which follows of some preferred embodiments thereof, provided by way of
example and also illustrated in the accompanying drawings in which:
Fig. 1 is a diagram showing three exemplary curves illustrating the rotation speed
of the sley cam against time;
Fig. 2 is a diagram showing three curves for acceleration of the sley, corresponding
to the curves of Fig. 1;
Fig. 3 is a diagram showing three curves for the displacement of the sley, corresponding
to the curves of Fig. 1; and
Fig. 4 is a diagram showing three curves for the linear speed of the sley, corresponding
to the curves of Fig. 1.
Detailed description of some preferred embodiments
[0025] Reference looms which can be used to implement the teaching of the present invention
are for example those described in the application EP 01830717.7 or in EP-A-1,158,081,
which documents are understood as being included here by way of reference. Consequently,
the general structure of such a loom will not be described in detail.
[0026] According to the invention, the direct-drive motor for driving the main components
of the loom is controlled and regulated so as to vary the speed according to different
criteria, with the aim of taking into account the effect on the actuated components
in mechanical and weaving terms, without however neglecting the aspect of energy efficiency.
[0027] According to a first embodiment, the speed of the direct-drive motor of the loom
is varied according to a given motion law which is identical for each cycle.
[0028] In a first case, the speed law is defined so as to control in the desired manner
a specific weaving component, for example the motion of the gripper couple of a gripper
loom.
[0029] Consequently, the grippers may for example be controlled by means of a screw device
having a constant instead of variable pitch, while the optimised motion law during
insertion is achieved by means of adjustment of the motor speed. Moreover, a corresponding
specific cam profile for actuation of the sley and the weaving machine is designed,
so as to obtain the desired optimum motion laws.
[0030] In a second case, the motor speed law or profile is defined so as to optimise the
behaviour of the loom, mainly in weaving terms.
[0031] Advantageously, in the case of an air jet loom, it may be envisaged, according to
the invention, slowing down the speed of the main motor during insertion of the weft
yarn. Slowing down during the insertion phase results in the advantage of greater
time available both as regards the sley and as regards the weaving machine, in particular
for those articles where crossing-over of the warp yarns does differ greatly, in terms
of phase, from beating-up of the reed.
[0032] In any case, an example of a law profile may envisage a linear behaviour of the speed
of rotation, with a maximum at beating-up (0° of the loom) and minimum at 180° of
the loom. In this way the required motor torque is constant with a deceleration from
0° to 180° and constant with an acceleration from 180° to 360°.
[0033] This basic law may then be modified to include several variations in speed of different
amount and also different shape (sinusoidal, polynomial).
[0034] As can be understood, in the first case mentioned relating to a gripper loom, the
solution of the invention results in considerable advantages in terms of mechanical
simplification, flexibility of use (hence greater rapidity in change-over of the article),
reduction in costs; the constant-pitch screw already per se offers a clear benefit
compared to a variable-pitch screw, with an improvement in the sliding block/screw
connection with lower hertzian pressures and therefore an increase in the reliability
(i.e. less play resulting from wear and greater duration); in the second case mentioned,
advantages in terms of productivity and yield are obtained.
[0035] According to a further embodiment, the speed law is varied from one cycle to another.
[0036] For example, in an air jet loom, a device for controlling the arrival of the weft
is provided, said device comprising two photocell sensors by means of which it is
possible to detect deviations of the real values of the weft arrival time from the
estimated values. By processing these values over time it is possible to define a
behaviour curve for the arriving weft yarn (depending on environmental factors, physical
characteristics of the reel, etc.) on the basis of which suitable variations to the
speed of the motor may be introduced.
[0037] In particular, in the case where an increasing delay in arrival of the weft yarn
with respect to the reference phase of the operating cycle is detected, it will be
possible to modify the speed profile of the motor so as to provide a slowing down
phase in correspondence of the weft insertion.
[0038] If, moreover, an air control device is provided on the air jet nozzle, it is possible
to co-ordinate the variation in speed of the motor with flowrate and insertion duration
parameters within the permitted maximum values for the specific yarn.
[0039] The modifications of the speed of the motor over time may moreover be defined on
the basis of suitable statistical functions which use as a parameter, in addition
to the shed opening times and to the signals supplied by the weft arrival sensor,
also an index relating to the number of weft breakages over time. Once in possession
of the inventive teaching offered here, any person skilled in the art is able to suitably
adapt these statistical functions for regulating the motion law.
[0040] Due to this further feature, it is possible to take into account, for example, the
frequency of breakage of the warp yarns and, especially in a gripper loom, the ratio
between the breakages in the side zones and the total breakages. This ratio is a measure
of an existing damaging interference between the grippers and the mouth of the warp
shed: by means of suitable adjustment of the speed profile it is instead possible
to solve this problem by varying the motion profiles of the weaving machine, performing
more or less rapid raising of the warp yarns, again by modifying the speed motion
of the weaving machine motor.
[0041] According to yet another embodiment, the loom is equipped with a dual drive system,
namely it has a first motor for the main weaving components (for example sley for
the air jet loom; sley and gripper for the gripper loom) and a second motor for the
weaving machine, both being mounted with a direct drive system. Preferably the first
motor is designed to "track and follow" (positionwise or speedwise) the second motor,
whereby the latter must normally have a greater power.
[0042] As a result of this arrangement, it is possible to achieve an even greater flexibility
since further mechanical connections are eliminated and therefore results in the speed
control of the first unit being independent of that of the second unit. The two motors
are connected together in a non-mechanical manner - by means of an electronic control
unit - and therefore it is very easy to adjust the individual operating profiles.
[0043] It is thus possible to obtain, in addition to the advantages already seen above in
the case of an individual motor, a wide range of variations in speed of the motor
of the weaving machine (and optionally, but not necessarily of the loom also) so as
to provide the most suitable motion laws depending on the different articles; it is
possible to obtain, for example, a more or less marked separation of the warp yarns
depending on the type of yarn or the article to be woven.
[0044] Advantageously, according to the method of the invention, said variations in speed
of the two independent motors of the loom and the weaving machine are correlated with
the statistical data as to the type and number of weft/warp breakages detected by
the control system.
[0045] It must also be pointed out that, according to the state of the art, the motions
of the warp yarns - defined by means of the weaving machine - are more or less rapid
as a function, among other things, of the various articles. Said motions are obtained
at present by means of special mechanisms of the weaving machine (cams for dobbies
and external gears, jacquard modulators, etc.).
[0046] According to the invention, a variable speed profile is employed, with a - for example
- linear, sinusoidal or polynomial profile, so that it is possible to obtain different
motions of the warp yarns by modifying the parameters of the motor instead of replacing
the abovementioned mechanisms (cams, etc.).
[0047] It must be pointed out that the variation in the motor motion law is suitably set
as a compromise between the various requirements, which include minimising the torques
to be applied to the motor, not exceeding certain load limits in the dynamic behaviour
of the system, and optimising the motion laws of the various weaving components (grippers,
reed, weaving machine).
[0048] Some possible examples of the speed variation, with the associated implications,
are provided below.
[0049] In an air jet loom, with a separate dual drive system, having an average speed of
970 rpm, a speed variation of +/- 30 rpm was obtained with a brushless motor having
a nominal torque of 30 Nm. Considering that the time allotted to weft insertion is
half the cycle (180 loom degrees), it was possible to achieve a deceleration, in the
same half cycle, equal to 1.5% in the case of a linear variation; in the case of a
sinusoidal variation, this deceleration was as much as 2.2%; it should be noted that
a percentage of 2.2% corresponds to about 4 loom degrees at the average speed of 970
rpm.
[0050] At the same average speed of 970 rpm, a variation in speed of +/- 150 rpm (which
requires a nominal torque of the motor equal to about 100 Nm) produces a deceleration
equal to 7.7% in the case of a linear variation and a deceleration of 12% in the case
of a sinusoidal variation (corresponding to about 18 degrees or 4 milliseconds at
the average speed).
[0051] The percentage decelerations (during the weft insertion phase) correspond to an equal
percentage increase in the loom throughput value.
[0052] The motion law of the sley vary as a result of the sinusoidal variations above mentioned
according to the curves shown in the accompanying figures.
[0053] As can be understood, with the method according to the invention it is possible to
achieve a series of advantageous results in connection with the problems encountered
in the prior art.
[0054] A variation in the motion of the loom is produced in such a way as to allow optimum
operation of the various weaving components, therefore making it possible to achieve
a textile product having an improved quality and lower cost.
[0055] In particular, it is possible to reduce the speed of the loom during the weft insertion
phase, so as to maintain an average speed over the loom cycle higher than the speed
in the insertion phase, with the advantage of an increase in productivity.
[0056] As a result of the novel technique described here, it is also possible to perform
a change-over of article without having to mechanically modify the loom, but by simply
varying some parameters from a control panel (console), with an obvious advantage
in terms of flexibility of use.
[0057] Moreover an operational flexibility of the weaving machine is achieved such that,
ultimately, the motion profile of the warp yarns may be modified depending on the
various articles, whilst maintaining overall a high productivity.
[0058] Furthermore, according to the method of the invention it is possible to relate the
variation of the speed profile (for example of the weaving machine of a dual-drive
gripper loom) to statistics relating to breakage of the warp yarns (in particular
to the ratio of breakage in the side zones to the total yarn breakages), said statistics
being determined by means of a controller device.
[0059] It is understood, however, that the invention is not limited to the embodiments illustrated
above, which represent only non-limiting examples of the scope of the invention, but
that numerous variations are possible, all within the reach of a person skilled in
the art, without thereby departing from the scope of the invention.
1. Weaving loom comprising at least one weaving machine, a sley, weft inserting members,
and a main motor driving at least the sley and the weft yarn inserting members, characterized in that said motor operates at a variable speed on the basis of predetermined textile requirements.
2. Loom according to Claim 1, in which said speed of the motor is variable within each
loom operating cycle.
3. Loom according to Claim 1 or 2, in which said speed of the motor is variable over
several successive operating loom cycles.
4. Loom according to Claim 1 or 2, in which the speed of the motor is variable within
each operating loom cycle depending on the individual different wefts to be inserted.
5. Weaving loom according to Claim 2, 3 or 4, in which a second motor mechanically independent
of the main motor is also envisaged for driving the weaving machine, said second motor
also operating at a variable speed on the basis of predefined textile requirements.
6. Loom according to any one of the preceding claims, in which said variable speed follows
a law profile such that, with respect to a nominal speed of rotation of the motor,
a deceleration during insertion of weft yarn is provided.
7. Loom according to any one of Claims 2 to 6, in which said variable speed follows a
linear function against time.
8. Loom according to any one of Claims 2 to 6, in which said variable speed follows a
polynomial function against time.
9. Loom according to any one of Claims 2 to 6, in which said variable speed follows a
sinusoidal function against time.
10. Loom according to any one of the preceding claims, in which said loom is of a gripper
type and the speed profile of the main motor is set on the basis of the speed profile
required by the grippers, the motion of other weaving members being determined by
means of cam systems or equivalent kinematic mechanisms as a function of said set
speed profile of the main motor.
11. Loom according to any one of the preceding claims, further provided with a device
for detecting the arrival time of the weft yarn, said device being able to detect
the timing shift of the weft arrival time, the speed profile of the main motor being
adjusted on the basis of said detected timing shift.
12. Loom according to any one of the preceding claims, in which said variable speed profile
of the motor is also set on the basis of the signal supplied by a yarn breakage detector.
13. Loom according to Claim 12, in which the signal of said yarn breakage detector is
a weighted function of the statistical number of breakages of yarns in relation to
their distance from the side zones of the fabric.
14. Method for controlling weaving operation of a loom provided with at least one weaving
machine, a sley, weft inserting members and a main motor for driving at least the
sley and the weft yarn inserting members, characterized in that said main motor is operated by varying the speed thereof on the basis of predetermined
textile requirements.
15. Method according to Claim 14, in which said main motor speed is varied within each
operating weaving cycle.
16. Method according to Claim 14 or 15, in which said variation in the motor speed is
modulated over a time frame including several successive operating weaving cycles.
17. Method according to Claim 14 or 15, in which the motor speed is varied within each
operating cycle depending on the individual various wefts inserted.
18. Method according to Claim 15, 16 or 17, in which the speed of a second motor mechanically
independent of the main motor and allotted to the weaving machine operation is also
varied.
19. Method according to any one of Claims 14 to 18, in which said motor speed is varied
following a profile speed such that, compared to a nominal speed of rotation of the
motor, a slowing-down during insertion of the weft yarn is produced.
20. Method according to any one of Claims 14 to 19, in which said slowing-down, and subsequent
speeding-up, is achieved through a linear function.
21. Method according to any one of Claims 14 to 19, in which said slowing-down, and subsequent
speeding-up, is achieved through a polynomial function.
22. Method according to any one of Claims 14 to 19, in which said slowing-down, and subsequent
speeding-up, is achieved with a sinusoidal function.
23. Method according to any one of Claims 14 to 22, in which said speed of the main motor
is varied following a profile based on the requirements of the weft insertion device,
the motion law of other weaving members being determined depending on said main motor
speed profile.
24. Method according to any one of Claims 14 to 23, in which the following steps are also
performed:
- detecting the performance characteristics against time of the weft yarn;
- establishing the arrival time of the weft yarn on the basis of said detection;
- modifying the speed profile of the main motor on the basis of said determination.
25. Method according to any one of Claims 14 to 24, in which the following steps are also
performed:
- detecting the number of breakages of yarns over time;
- modifying the speed profile of the main motor on the basis of said detection.
26. Method according to Claim 25, in which the step of modifying the speed profile of
the weaving machine motor on the basis of said detection is also provided.
27. Method according to Claim 25 or 26, in which said detecting step further comprises
determining a breakage parameter in the form of a weighted function of the statistical
number of weft breakages in relation to their distance from the side zones of the
fabric.
28. Method for controlling a weaving loom equipped with two motors for driving respectively
a weaving machine and weaving members, said weaving members being at least the sley
and optionally a weft inserting device, characterized in that said motors are operated by varying the speed thereof within the weaving cycle on
the basis of predetermined textile requirements.