INSERTION SYSTEM OF THE WEFT THREADS IN A WEAVING LOOM

Abstract

 Weft thread insertion system into a projectile weaving loom, wherein the projectiles (1) are launched into the shed due to the mechanical action of a thrust member provided with alternate cyclic movement consisting of a rack (R) driven into motion by a plurality of toothed wheels (D), each one controlled by a respective electric servomotor (M), arranged in succession along the rack (R) and meshed therewith.

Description

[0001] The present invention relates to an insertion system of the weft threads in a projectile-type weaving loom and in particular to a projectilelaunching device.

FIELD OF THE INVENTION

[0002] As known, projectile weaving looms differ from the other types of weaving looms due to the fact that the weft threads are inserted into the shed through a projectile, that is, a tapered metal body of suitable mass and shape, to which - before performing the launch, and hence to a stationary projectile - the end of the weft thread is fastened.

[0003] At the shed exit (usually in correspondence of the right hand side of the weaving loom, with reference to the weaver's position) the projectile is slowed down and halted by a braking device, the weft thread is unfastened and hence the projectile is caused to return towards the launch side of the weaving loom (usually the left hand side) through a suitable continuous transport system. On the launch side, the single in-coming projectiles are loaded onto a device which progressively brings them in front of the launchings station where they are again fastened to a desired weft thread and launched again into the shed.

[0004] This type of weaving loom, in the light of advantages detectable especially in the weaving of very high fabrics, has some significant drawbacks.

STATE OF THE PRIOR ART

[0005] Firstly there are drawbacks of a mechanical type, directly connected to the high impulse thrust which must be imparted to the projectile. In particular, in addition to the problems determined by the impact which the projectile receives by the launching member, the complication remains of devising a suitable mechanism which produces a sufficiently intense but not excessively invasive impulsive thrust.

[0006] GB 2,003,198 discloses a conventional launching device wherein a launch member, meant to abut strongly on the rear end of the projectile, is supported on a lever controlled by a torsion bar cyclically loaded through a cam mechanism.

[0007] As can be easily guessed, the cam-loaded torsion bar system represents a rather critical mechanical component, both in terms of the stresses undergone and imparted, and in terms of the opportunity to determine and control the law of motion of the projectile in the launching step.

[0008] As a matter of fact, since the projectile is launched through the shed with a very high impulsive acceleration, and is not subsequently controlled by any control member, in the projectile weaving looms some typical weaving problems arise and in particular a high initial stress of the weft threads and a substantially uncontrolled behaviour of the projectile along the entire travel within the shed. In particular, when the thrust impulse does not occur in a perfectly symmetrical manner on the projectile, the projectile trajectory undergoes lateral oscillations which are controlled by the guides within which the projectile slides but which impair launch effectiveness and regularity.

[0009] EP-1591573 discloses an alternative solution for the projectile launch, wherein the projectile is brought to the maximum set speed no longer due to an impact effect, but rather through the progressive thrust imparted thereto by an insertion tape. Said tape is controlled through a device similar to the one already in use for gripper movement in gripper looms, suitably modified to cause the accelerations which are necessary for launching the projectile. Such device comprises a toothed wheel meshed in corresponding holes formed along the insertion tape - which tape is flexible to allow a sufficiently wide winding arc on the toothed wheel - the toothed wheel being controlled in alternate rotation by the main movement of the loom through a double desmodromic cam connected to an articulated quadrilateral consisting of rocking arm, connecting rod and toothed sector coupled with a pinion which is integral with and concentric to the toothed wheel.

[0010] After the initial launch step, the tape is progressively slowed down and caused to go back in, while the projectile continues the travel thereof by inertia, completing the insertion of the weft in the traditional way in use in projectile weaving looms.

[0011] The technical solution disclosed by patent '573 allows, at least from a theoretical point of view, to overcome the above-described drawbacks of projectile weaving looms with torsion-bar launching device. As a matter of fact, the acceleration induced by such launching device is much more gradual than that of the conventional twisting-bar device and, moreover, the projectile is constantly led by the tape as far as inside a first shed portion and thus acquires a much more stable trajectory than that of the known launching system.

[0012] However, despite these positive features, such launching system of the projectiles has not found so far an effective industrial application due to the fact that the high inertia of the mechanical control of the above-described toothed wheel limits the motion inversion speed thereof to such values which do not allow the building of projectile weaving looms having a suitable weft insertion speed (number of cycles per minute) with respect to that of the other weaving looms found on the market.

BRIEF DESCRIPTION OF THE INVENTION

[0013] The present invention hence lies in the same technical sector which has been described in connection with patent '573, with the object of providing a weft insertion system in a projectile weaving loom which is devoid of the problems highlighted by the known above-illustrated solution as regards the opportunity of reaching a weft insertion speed which is competitive with the known-type weaving looms currently on the market.

[0014] This object is achieved through a weft insertion system in a projectile weaving loom having the features defined in claim 1. Other preferred features of such weft insertion system are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Further features and advantages of the weft insertion system in a projectile weaving loom according to the present invention will anyhow be more evident from the following detailed description of a preferred embodiment of the same, provided as a mere non-limiting example and illustrated in the attached drawings, wherein:

fig. 1 is a schematic perspective view of the projectile launching device;

fig. 2 is an overall schematic and partly section view of the entire weft insertion system according to the present invention; and

fig. 3 is an angular diagram of the characteristic phases of the system of fig. 2, with reference to a weft insertion cycle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] According to the present invention, in order to solve the above-highlighted problem with a solution which is simple from a construction point of view and of immediate application, the projectile insertion member 1 consists of a rack R driven into motion by a plurality of toothed wheels D, arranged in succession along the development of rack R and meshed therewith, each of wheels D being driven by a respective electric servomotor M, for example of the brushless, electronic-control type. Rack R has a rectilinear layout and has a rigidity sufficient to transmit to projectiles 1 the thrust impressed by wheels D without undergoing significant deformations.

[0017] The number of motors M and the arrangement thereof along rack R may be varied at will depending on the overall desired power, on the maximum power which can be effectively released by a single motor onto the teeth of wheels D simultaneously engaged with corresponding cavities of rack R and, furthermore, on the space available beside the loom. In particular, from this point of view, motors M can be arranged aligned on one side only of rack R and below it, as illustrated in fig. 1, or on both sides or rack R in an alternate or opposite arrangement, or else both above and below rack R in a mutually offset arrangement so as to optimise space use and to reduce the necessary length of rack R, the number of cavities of the same in simultaneous engagement with wheels D being the same.

[0018] Due to the fact that the power necessary to obtain the desired acceleration of rack R has been divided onto multiple electric motors M, it is possible to use motors M having a very modest rotor size, and hence having each a very low rotation inertia. Motors M having this low inertia hence allow to achieve extremely low motion inversion times and, accordingly, to perform a high number of cycles of weft insertions in the loom.

[0019] According to a preferred feature of the invention, the electronic control of motors M is performed differently between one of motors M which is considered the main motor, and the remaining motors M which are considered motors enslaved to the main motor. In particular, said electronic control is performed by controlling the main motor in position, so as to obtain the desired motion curve of rack R within a weft insertion cycle. The torque developed by the main motor as a consequence of such law of motion is read and instantly "copied" onto the remaining enslaved motors, which hence all work with the same torque as the main motor.

[0020] Due to this particular type of electronic control, any possible position misalignment between the different motors M is avoided, which motors, as a matter of fact, all impart the same torque onto rack R, while the position of said rack is controlled by the sole main motor. The thrust expressed by the assembly of motors M is thus perfectly evenly divided among all the teeth of wheels D in engagement with respective cavities of rack R eliminating any possible stress variation on the individual teeth which would instead easily occur if the electronic control were a simple position control on all motors M, considering the difficulties of obtaining a perfect synchronism of such multiple position control.

[0021] Fig. 2 shows a weft insertion system on the whole which comprises, in addition to the above-described launching device, and in a way known per se, a weft feeder F which feeds weft W to a weft selector P which displaces the weft of interest onto the launch path of a projectile 1 thrust by rack R. Weft W is fastened in flight by projectile 1 according to the ways already known for the carrying gripper of gripper looms and hence projectile 1 is launched in the shed along guides G by the action of rack R.

[0022] When the speed of projectile 1 has reached the desired value, rack R begins the deceleration, halt and return-to-the-starting-position phase, while the projectile proceeds due to its inertia as far as the exit side of the loom where it goes through a gripper-opening device 2 which releases weft W and a projectile braking device 3. The projectile hence enters a suitable housing of an unloading device 4 - of which, for greater clarity, a front view is also given, in the lower part of fig. 2 - provided with two opposite housings in the illustrated embodiment, actuated by a motor 5 which provides to cause unloading device 4 to rotate by 180° on an axis parallel to the projectile trajectory, bringing the projectile in correspondence of a projectile return device.

[0023] Here such return device - fully similar to the launching one, but provided with a single motor M_R and respective toothed wheel D_R which actuates a rack R_R _ provides to cause projectiles 1 to return, launching them along a return track 6 at reduced speed with respect to the forward speed, as far as the launch side of the loom. Projectiles 1 are halted here by a braking device 7 and brought into the chosen drawing position by a cursor moving-back device 8, which causes projectiles 1 to move back up to the working area of a loading device 9.

[0024] Loading device 9 and the relative actuation motor 10 have a layout, operation and graphic representation fully similar to the ones described above for unloading device 4, with the only difference that the number of housings for the projectiles 1 of loading device 9 is twofold compared to that of unloading device 4 (in the embodiment illustrated there are hence four housings offset by 90°). Said layout allows to receive in loading device 9 up to 4 projectiles, since the time employed by the projectiles to travel the return track is about twice that employed in the forward phase and hence more than one projectile can be simultaneously in transit along return track 6. As a result, in case of machine halt, loading device 9 must be able to house all the projectiles already sent into the return track.

[0025] A preferred operation cycle of the weft insertion system, expressed in angular coordinates for a weft insertion cycle (360°), is illustrated in fig. 3 and provides the following characteristic phases:

0° - projectile acceleration start

60° - weft cut

65° - rack entry into the shed and deceleration start

115° - rack return start - projectile in flight

300° - projectile arrival and rack repositioning

360° - projectile braking and insertion into the unloading device.

[0026] However, it is understood that the invention must not be considered limited to the special arrangements illustrated above, which are only exemplifying embodiments thereof, but that different variants are possible, all within the reach of a person skilled in the field, without departing from the scope of the invention, which is exclusively defined by the following claims.

Claims

1. System for the insertion of weft threads in a projectile weaving loom of the type in which the projectiles (1) are launched into the shed due to the mechanic action of a thrust member provided with alternate cyclic movement, characterised in that said thrust member consists of a rack (R) driven into motion by a plurality of toothed gears (D), each driven by a respective electric servomotor (M), arranged in succession along the rack (R) and meshed therewith.

2. System for weft thread insertion as in claim 1, wherein the rack (R) has a rectilinear shape and sufficient rigidity to transmit to the projectiles (1) the thrust imparted thereto by the wheels (D) without deformations.

3. System for weft thread insertion as in claim 2, wherein the number of the motors (M) is calculated according to the overall desired power and of the maximum power which can be effectively released by a single motor onto the teeth of the wheels (D) simultaneously engaged with corresponding cavities of the rack (R).

4. System for weft thread insertion as in claim 3, wherein said motors (M) are arranged in succession on one side or, alternated or opposite, on both sides of the rack (R).

5. System for weft thread insertion as in claim 3, wherein said motors (M) are arranged alternated above and below the rack (R) and on one or both sides of the same.

6. System for weft thread insertion as in claim 2, wherein the electronic control of the motors (M) comprises a position control of one of said motors, considered as main motor, for determining the desired movement curve of the rack (R) within a weft insertion cycle, and a torque control of the remaining motors, for adjusting the torque thereof to a value identical to the instantaneous torque value applied to the main motor.

7. System for weft thread insertion as in any one of the preceding claims, furthermore comprising a loading device (9) and an unloading device (4) arranged upstream and downstream, respectively, of the loom in the direction of the weft thread insertion (W) and each provided with housings for the projectiles (1), respective driving motors (10, 5) being further provided for actuating the rotation of said loading device (9) and unloading device (4) around axes parallel to the projectile launch trajectory between preset angular positions in which said housings for the projectiles (1) are flush with the guides (G) of the projectiles (1) or with a return track (6) of the projectiles (1) which connects the unloading device (4) to the loading device (9).

8. System for weft thread insertion as in claim 7, wherein the loading device (9) has a number of housings for projectiles (1) equal to or larger than the overall number of projectiles simultaneously in transit on the guides (G) and on the return track (6).

9. System for weft thread insertion as in claim 7, wherein the projectiles (1) are launched on the return track (6) through a launching device similar to the main launching device and comprising a single motor (M_R) and respective toothed wheel (D_R) which actuate a rack (R_R).

Drawing