The present invention refers to a control leverage mechanism for tuck-in devices meant for weaving machines and in particular to tuck-in devices the operating head of which alternately moves in the warp direction, during each weft insertion cycle.
The selvedge-forming devices, briefly referred to in the sector as "tuck-in devices" consist of mechanical, electric, pneumatic devices, or combinations thereof, which are used in shuttle-less weaving looms for forming a false selvedge (thus defined in opposition to the true selvedge which is formed in shuttle weaving looms) along the lateral edge of the fabric being woven, steadily fastening the weft tails which laterally protrude from the cloth being woven, after the insertion and cutting of the weft yarns.
This operation is performed through an operating head of the tuck-in device which, in various possible operating modes, of a mechanical, electronic, pneumatic or mixed type, grabs the free weft tail of the last inserted weft, immediately after the closing of the shed and the beating of the reed against such weft, and immediately inserts it back into the shed, thus anticipating both shed closing and the reed beating-up on the subsequent weft, so that said weft tail is steadily retained in position among the warp yarns together with said subsequent weft, thus causing selvedge forming, as an alternative to the free fringe of weft tails, with remarkable advantages in terms of stability and resistance of the fabric edges during the subsequent processing and handling of the fabric.
Tuck-in devices are more frequently provided with a fixed operating head and they are positioned at the two sides of the cloth being woven next to the reed. Since one or more pieces of a reduced width are often simultaneously woven on the loom width, in order to allow the positioning of the tuck-in devices with fixed operating head within the loom shed, it is of course necessary to shorten or cut the reed into two or more segments, since, in the contrary, a mechanical interference would occur between the reed and the tuck-in device during reed movement.
Tuck-in devices with travelling operating head solve this problem due to the fact that the travelling head thereof is provided with an alternate movement in the direction of the warp yarns, which movement allows the backward travel of said operating head during reed beating-up and the subsequent quick forward travel of the same in the immediately subsequent step. It is hence possible to operate with these tuck-in devices with a whole reed, that is, a reed which extends across the entire loom width, regardless of the size and of the number of cloths simultaneously processed on the loom.
Tuck-in devices with a fixed head of a different structure and actuating system are disclosed for example in
Well-known in the field is then a tuck-in device with a travelling head manufactured by SULTEX AG, which does not seem having been patented, wherein the movement of the operating head of the tuck-in device, travelling along linear sliding guides, was derived from the main movement of the loom (and in particular from the movement of the sley) through a kinematic mechanism comprising an articulated quadrilateral and a cam apt to determine the particular desired motion law of the operating head of the tuck-in device.
To the travelling head of the above disclosed tuck-in device , a weft-cutting device was furthermore made integral, according to an arrangement already known for a long time, so that said device follows the head of the tuck-in device in the alternate movement thereof in a longitudinal direction, to be able to perform weft cutting at the selected time, after the insertion of said weft into the shed. The control of the above-said cutting device was independent from the control of the travelling head of the tuck-in device and was normally entrusted to a pneumatic or electric device.
The technical solution disclosed by the Sultex travelling-head tuck-in device, briefly described above, has some mechanical drawbacks which the present invention aims at overcoming.
A first critical point of the control of the travelling head of the tuck-in device illustrated above consists in the linear guides on which the travelling head of the tuck-in device slides. As a matter of fact, these guides are sensitive components which generally require, in order to provide regular performances and a satisfactory life duration, a lubrication system or, at least, regular greasing operations, in order to avoid too quick a wear with the forming of plays which reduce the reliability of the device.
A second critical point can be identified in the cam system per se, linked to the need to provide a suitable lubrication, or at least a regular greasing of the cam-follower rollers. Such rollers then present serious reliability problems in this type of applications.
Finally, a third drawback is linked to the necessary provision of a separate control for the weft cutting device. As a matter of fact, pneumatic cutting devices have response delay problems which complicate the management of such devices; this problem does not arise in the case of the employment of an electrical servocontrol, which, however has high costs and is demanding from the point of view of the hardware and software implementation.
A first object of the present invention is hence to offer a travelling-head tuck-in device provided with a new-concept control which does not require the use of cylindrical guides to obtain the alternate translation movement of the travelling head.
A second object of the present invention is the removal of a system which provides the use of any cam system for generating the alternate motion of the travelling head.
A third object of the present invention is then to offer a tuck-in device wherein the execution of the weft cut may be performed without the use of pneumatic or electric actuators and hence allows a simpler, more effective and cheaper construction.
All these objects are achieved, according to the present invention, through a weaving loom comprising a sley and a travelling-head tuck-in device comprising a control leverage mechanism having the features defined in claim 1. Other preferred features of such control leverage mechanism of a tuck-in device are defined in the dependent claims.
Further features and advantages of the control leverage mechanism of a tuck-in device according to the present invention will in any case be more evident from the following detailed description of a preferred embodiment of the same, provided purely as a non-limiting example and illustrated in the attached drawings, wherein:
In the following description, when the terms forward and forward movement are used it is meant to refer to the progression direction of the fabric on the loom, represented in the drawing by arrow T. The terms backward and backward movement indicate of course the opposite direction.
In a first embodiment, the control leverage mechanism of a tuck-in device according to the present invention, in order to achieve the first and the second object highlighted above, consists of the following functional groups of levers, highlighted in
According to a main feature of the invention, said first rod-crank mechanism G1 lies at the dead point thereof when the travelling head of the tuck-in device is at the backward operating position thereof.
According to another feature of the invention, the connecting rod of said rod-crank mechanism G1 has a longitudinal movement having a direction consistent with the movement of the sley S.
In a second embodiment, the control leverage mechanism of a tuck-in device according to the present invention, in order to achieve the third object highlighted above, furthermore comprises the following functional group of levers:
According to a feature of the invention said weft cutting device furthermore comprises a fixed cutting blade, integral with the travelling head of the tuck-in device.
The functional groups of levers defined above will now be described in greater detail with reference to the drawings wherein, for greater clarity the references of the individual levers are indicated in
The first articulated quadrilateral Q1 consists of the sley S, of a forward-transmission connecting rod LF and of a lever L1 hinged in A to the body CC of the tuck-in device and hence comprises two hinges 1 and A fixed with respect to the loom, and two moving hinges 2 and 3.
Rod-crank mechanism G1 consists of a lever L2 and of a backward-transmission connecting rod LR hinged in B on the travelling head LC of the tuck-in device and hence comprises a fixed hinge A and two moving hinges 4 and B. Levers L1 and L2 hinged in A form with each other a suitably determined fixed angle.
Parallelogram P1 consists of a pair of identical and mutually parallel levers LP; said levers are hinged in 5 and 6 to the body CC of the tuck-in device and in 7 and 8 to the travelling head of the tuck-in device, schematised in the
Finally, the second articulated quadrilateral Q2 consists of a first lever L3, of an upward-transmission connecting rod LH and of a lever L4 integral with a moving cutting blade 9. Said cutting blade 9 forms a weft cutting device together with a fixed cutting blade 10 which is integral with the travelling head LC of the tuck-in device. Lever L3 is integral with backward-transmission connecting rod LR and consists in an extension thereof beyond hinge point B of the same. The second articulated quadrilateral Q2 hence comprises two hinges B and C, fixed with respect to the travelling head LC of the tuck-in device, and two moving hinges 12 and 13.
From the functional point of view, the leverage mechanism of the present invention illustrated above has the features indicated in the following.
The first articulated quadrilateral Q1, which has the function of taking the movement from the sley S for generating the rotation of the lever L1 on hinge A, has a similar structure to that of the known devices mentioned in the introductory part.
Rod-crank mechanism G1 provides to transform the rotary motion of lever L1 into a translation movement of connecting rod LR. The movement of such lever has the feature of being consistent with that of the sley, and can hence be directly used for generating a movement of the travelling head of the tuck-in device synchronous with that of the sley, and furthermore it exploits - through an adequate choice of the angle between levers L1 and L2 - the dead point position of the rod-crank mechanism for generating an almost stationary condition at the point of utmost backward movement, that is an area where, despite continuing the movement of the sley S, the travelling head LC of the tuck-in device is virtually stationary and can hence correctly perform the operation of insertion of the weft tail into the shed.
It must be noticed that the kinematic mechanism described above is an excellent approximation of the ordinary rod-crank mechanism with linear guides of the prior art, since hinge B does not follow a rectilinear motion but moves along an arc determined by parallelogram P1.
In the comparison with the solution of the prior art, the movement of the rod-crank mechanism G1 replaces that of a conjugated cam; a relatively complex and costly mechanism comprising highly critical members from the point of view of reliability, such as cam-follower rollers, is hence replaced by a much simpler and more reliable mechanism.
Articulated quadrilateral Q2 exploits the further rotation of lever L3 on hinge B, during the almost stationary condition step of connecting rod LR along the longitudinal direction, for generating the rotation of lever L4 on hinge C, which hence operates the moving cutting blade 9.
It must be noticed that the connecting rod LH of articulated quadrilateral Q2 is of an adjustable length, for example through an eccentric, so that it is easily possible to change the initial angular position of lever L4 and hence the adjustment of the cutting instant.
As stated, the rotation of lever L3 on hinge B occurs mostly when rod-crank mechanism G1 is in the dead point area and hence precisely in the time period in which the travelling head LC of the tuck-in device is almost stationary and the cutting device must operate.
Rod-crank mechanism G1 hence performs a twofold function, exploiting in two different ways the dead point area thereof, that is for determining first an almost stationary condition of the travelling head LC of the tuck-in device and, in such step, for continuing the rotation to operate the cutting device through the articulated quadrilateral Q2.
This part of the leverage mechanism of the present invention hence replaces the independent operation of the weft cut, with an obvious and considerable reduction of the complexity and of the cost of the mechanism.
Parallelogram P1, used about the quadrature thereof, allows to the travelling head LC of the tuck-in device a movement along a sufficiently wide arc which can be approximated to a rectilinear movement. This part of the leverage mechanism hence replaces the cylindrical guides of the known devices, with an evident construction simplification and a dramatic reduction of maintenance interventions.
As a matter of fact, even assuming to provide the leverage mechanism with a guide apt to eliminate the possible modest lateral displacements of the levers, such guide could be used in the absence of any lubrication since, in the face of a null theoretical load, there is a very low actual load.
In designing the leverage mechanism of the present invention, the lengths and the positioning of the various levers have been optimised so as to obtain the desired movement of the leverage mechanism. In particular and in extreme synthesis:
The entire leverage mechanism is structured so as to allow the removal of the bearings, due to generally rather modest angular travels. This allows to further reduce the costs of the device and to further simplify the maintenance thereof.
However, it is understood that the invention must not be considered limited to the special arrangements illustrated above, which make up 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 protection of the invention, which is exclusively defined by the following claims.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.