Noiseless high-speed circular loom for producing tubular fabrics consisting of strips, threads and the like made of synthetic or natural materials

This invention relates to a circular loom for the continuous weaving of threads, strips, straps and the like made of any materials, preferably of plastic material, such loom being improved so as to allow high rotational speeds and consequently a high productivity, a particularly low noise index and a high technological and mechanical reliability.

As is known, the conventional circular looms for the manufacture of tubular fabrics consisting of straps or strips of plastic material, comprise two sets of heddles arranged on two concentric circles and subjected to reciprocating upward and downward movements to achieve an alternate spreading apart of the warp threads and so to create the so-called "wave shed"; the warp threads are guided through a cylindrical reed and are then deviated into a hollow vertical cylindrical body (fabric gauge), on the upper or lower circular edge thereof the fabric being formed due to the insertion of the weft threads among the warp threads.

The weft threads are fed by one or more shuttles, carrying on board thread bobbins, and are caused to rotate on the circular reed and are guided on the latter through proper guiding shoes. The shuttles, due to their rotation between the alternatively open zones of the warp threads, feed their own weft thread among said warp threads according to a spiral which closes on the edge of the vertical cylindrical body: by consequence the tubular fabric continuously forms on the circular edge of said cylindrical body, wherefrom it is continuously drawn and wound into bobbins.

The circular looms commercially available at present exhibit several limitations and drawbacks, out of which, chiefly, a low production speed (maximum speed: 150 r.p.m.), an excessive noise and a low autonomy of product fed to the bobbins.

In fact, the low speed depends on the presence of forces of inertia in the masses, subjected to the reciprocating motion, of the heddles and corresponding control kinematic motions, such forces of inertia limiting the stroke of the heddles and, by consequence, the dimensions of the opening sections of the wave shed and therefore also the transversal sections of the shuttles, with reduction of the weft bobbins capacities and so of the loom autonomy; furthermore the mechanical structure of said conventional looms is very complex and highly stressed, wherefore the mechanical reliability results to be remarkably reduced. Finally, the conventional circular looms are very expensive, exhibit a too high noise index and require a constant lubrication. A further limitation is due to the impossibility of carrying out crossings of warp threads with weft threads different from the simple crossing type, besides the drawback of having warp threads which are compelled to sweep the guide rings of the contiguous heddles, to the serious detriment of the integrity of the warp threads.

More particularly, the German Patent No. 1.257.069 discloses a circular loom for the manufacture of tubular fabrics in which the heddles (not shown in figures) are formed by metal bars and the magnetic means used for realizing an oscillating reed are of a complex mechanical structure which cannot allow high rotational speed and high productivity; furthermore, in said loom the presence of forces of inertia in the masses, subjected to the reciprocating motion, of the heddles and of their control kinematic means causes a great limitation of the stroke of the heddles and of the dimension of the wave shed to be obtained.

In the German Patent No. 2.921.988 it is also disclosed a circular loom which allows the same inconveniences and limitations as those of the loom of the above cited German Patent 1.257.069; in fact, the heddles are metal shafts having a great mass and the motion of the same is obtained by a set of levers guided within recesses forming cams, which cams are present on a rotating droom; this realization causes an excessive noise and a low autonomy of products supported by the bobbins and also requires a constant lubrification.

Finally, the French Patent No. 2.442.905 discloses a circular loom the mechanical structure of which, similarly to the previous Patents, involves great masses in all the oscillating and rotating devices so that the speed of the loom is very low and a constant maintenance is required. Thus, it is an object of the present invention to provide a circular loom for manufacturing tubular fabrics starting. from threads or strips of polymeric materials in general, which is structured in such manner as to obtain the alternate movement of the heddles, bearing the warp threads, by means of very reduced mass kinematic elements, so as to give free or release the motion of the heddles from the masses of their reciprocating control and guide members, which members, just due to their mass, remarkably limit the loom performances.

It is another object of this invention to provide a loom of the type specified hereinbefore, capable of effecting the alternate spreading apart of the warp threads by means of control and guide mechanisms subjected to a particular continuous undulatory motion such as to free the loom speed from any inertial stress and from the noise; in fact, failing any heavy members effecting reciprocating motions, the noise tends to disappear.

Still a further object is that of providing a circular loom of particular structural simplicity, high. reliability and moderate cost, such as to require very reduced maintenance works, no periodic lubrication and, above all, capable' of allowing the carrying out of more types of thread crossings for the manufacture of fabrics endowed with particular aesthetical effects.

A further object of this invention is that of providing along with said particular control-kinematic motion of the heddles, an efficient guide and control mechanism of the shuttles along the reed circumference, such mechanism consisting of guiding shoes and of wheels resting on the reed, suited to prevent any sliding friction between shuttles and reed.

The principle which the operation of the loom and in particular of the alternate or reciprocating spreading apart kinematic system of the warp threads, free from mechanical members affected by linear reciprocating motions, is based on, is theoretically similar to an undulatory reciprocating motion, corresponding to the one which in "Rational Mechanics" is defined as "movement of regular retrograde precession", the angular speed of which varies according to the sinusoidal law and therefore is such as to be free from high momentary variations. Such precessional movement is explained more in detail in the following.

The objects and advantages specified hereinbefore are achieved in practice by a circular loom for tubular fabrics prepared from threads and/or strips of polymeric materials, natural materials and the like, of the type equipped with heddles arranged on two concentric circles and with a central driving shaft, such loom providing, for the reciprocating spreading apart of the inner and outer warp threads, a supporting member, coaxially rotating around the central and vertical shaft of the loom, one or more pairs of wings or circular sectors preferably diametrically opposed to one another being coupled, under a predetermined and fixed angle of inclination in respect of the axis of said shaft, on said support, each pair of wings being coupled inclined on said supporting member with interposition of a roller bearing mounted on a cylindrical section on said supporting member, whose axis is inclined to the loom axis, so as to prevent said wings, through means effecting an oscillating connection of the wings with fixed parts of the loom, from rotating around said supporting member when the loom is working and so assuming a continuous undulatory motion, the end portions of said opposite and oscillating wings being connected, through a plurality of rods or the like, with eye-bearing elasting members acting as elastic heddles, so as to transfer the undulatory motion of said wings to said elastic heddles and therefore to obtain, along the development of the loom reed and by using more pairs of wings, the necessary spreading apart of the warp threads which is suited to form the wave shed, rolling means associated with conventional shuttles pushers, as well as multiple-wheel devices, suited to provide a support and a guide for the shuttles without sliding friction between shuttles and cylindrical reed being furthermore provided for the driving of the shuttles.

More particularly, said support member for said pairs of wings or circular sectors consists of a tubular shaft, coaxially rotating with the vertical shaft of the loom, on which as many coaxial bushes as the pairs of opposed wings are keyed, each of said bushes having its cylindrical outer surface inclined under a fixed angle in respect of the rotational axis of the loom shaft and of the bush-holding tubular shaft, on said cylindrical inclined surface a radial bearing being then mounted which, in its turn, carries a pair of opposite wings.

Still more in particular, said means for the oscillating connection of each oscillating wing with a fixed part of the loom consists of rigid locking means or of pendulum connections, capable of allowing said wings, when the loom is working, to oscillate in a substantially vertical plane without angular shiftings around the loom shaft, while said elastic eye-bearing members acting as heddles are made of steel wires, preferably angle bended and connected with a fixed part of the loom.

Always according to this invention, to obtain a configuration of the wave shed of the warp threads capable of reversing at every shuttle run, the tubular bush-holding shaft is subjected to a speed which is twice the one of the loom shaft when the loom is equipped with four shuttles, three times the one of the loom shaft when the loom is equipped with six shuttles; generally the speed variation will be determined by the following formulawherein N_b=number of revolutions of the bushes/ 1 minute, N=number of revolutions of the loom/1 minute, and K=number of shuttles.

The constructive and functional characteristics of the circular loom object of the present invention, relating to a preferred and not exclusive embodiment, are described more in detail hereinafter making reference to the enclosed tables of drawings, which are given for merely indicative but not limitative purposes, in which:

• Figures 1, 1a, 1b and 1c show the theoretical diagram of the prcession movement of three axes (in four angular positions) around other three fixed axes, suited to explain the alternate spreading apart of warp threads in the loom of the invention;
• Figure 2 shows, axially in section, an enlarged particular of the reciprocating spreading apart device of the warp threads, included in the circular loom according to the invention;
• Figure 3 shows a side view of a detail of the loom of the invention and exactly an elastic member with eye constituting a heddle for said loom;
• Figure 4 schematically shows an axial section of the circular loom of the invention;
• Figure 5 shows a plane development of the undulatory motion scheme of the wings or circular sectors and the successive (positive or negative) openings of the warp threads forming the wave pitch required for the penetration by the shuttles, and
• Figures 6 and 7 schematically show, in diametral section and in a plane-developed side view, the guiding and supporting devices of a shuttle on the cylindrical reed of conventional type.

As already explained hereinbefore, the principle on which the operation of the loom object of the present invention is based, and in particular the principle of the reciprocating spreading apart of the Warp threads, is similar to an undulatory motion corresponding to the regular precessional motion; such precessional motion is schematically represented in Figures 1 to 1_c, wherein four successive angular positions of a tern of axes rotating around another fixed tern are shown.

Therefore, with reference to Figures 1―1a― 1_b-1_c' if there are given a reference tern X, Y, Z fixed in space and a second tern X', Y', Z' integral with the first one in the common origin 0; but with axis Z' inclined under an angle a (in respect to Z), when axis Z' performs a rotatory motion in respect of Z, it will describe with the positive axis a conical surface having the concavity turned upwards and the vertex in 0; consequently, axes X' and Y', if kept unchanged in their orientation in respect of axis Z (and therefore always lying in planes X-Z and Y-Z), will be compelled, due to the rotatory oscillation of Z', to alternately oscillate upwards and downwards with harmonic motion, i.e. free from intense accelerations. Figures 1 to 1_c show four consecutive positions or orientations of axis Z' in respect of axis Z and, precisely, a starting position (Figure 1), at 90° in Figure l_a, at 180° in Figure 1_b and at 270° in Figure 1_c.

Supposing that axis Z is coincident with the axis of the loom (the circular loom is a machine with an axis of symmetry coincident with the axis of rotation), then it is sufficient to utilize the motion of the positive and negative ends of axes X' and Y'to achieve the reciprocating motion required to control the warp threads for the interlacement with the weft threads.

In practice, it is therefore possible to key, on the loom central shaft, bushes or analogous elements having the external surfaces with axes inclined as axis Z', to mount on said bushes radial bearings and to couple thereon two wings or opposed circular sectors, embodying axes X' and Y'; if said opposed and inclined wings are then held at their end portions for example by articulated pendulum connections or other oscillatory clamping means so as to remain in planes X-Z and Y-Z, an undulatory motion is obtained for said wings, which can be used to control elastic members acting as heddles.

The circular loom according to this invention is therefore designed by utilizing kinematic motions operating on the basis of the principle described hereinabove.

Making reference now to the above-mentioned figures, and in particular to Figures 2-3-4, the circular loom object of this invention is essentially of the type having a vertical central shaft 1, arranged coaxially with hollow body 2 which forms fabric 3 and driven by a geared motor 4 (Figure 4) through couples of gears 5―6. The spreading apart of warp threads 7, 8 etc. (Figure 4) is achieved, according to the present invention, by coaxially applicating to shaft 1 of the loom a hollow shaft 9 (Figures 2-4), driven independently of shaft 1 through a couple of gears 10-11, which are driven by said geared motor group 4; bushes 12, 13 etc., in a number fixed in advance on the basis of the number of shuttles, are keyed on hollow shaft 9, to attain a higher continuity of the wave sheds, as better explained in the following.

For simplicity's sake, two bushes 12-13 are shown in Figure 4.

Each bush is keyed on shaft 9 coaxially therewith and is designed so as to have its external cylindrical surface inclined under a prefixed angle (Figures 2 and 4) in respect of the axis of shaft 9; the angle of inclination is the same for all the bushes keyed coaxially with shaft 9, but the orientation or angular position or location of the one to the other is suitably offset depending to the number of bushes in order to achieve, as already mentioned, a good continuity of the wave pitch.

On each bush 1.3 (Figure 2) a roller bearing 14 is keyed and on this roller bearing a hub 14' holding two wings 16-17 diametrally opposed to each other is coupled; the. free end portions of said opposed wings are prevented from rotating around shaft 9 by pendulum-oscillating clamping means or the like, as schematically shown with 20 in Figure 4, wherefore, thanks to the presence of the bearing, the wings are capable of oscillating in substantially vertical planes without rotating.

The end portions of the wings are then each connected by a plurality of tie rods 21-22 and 23-24 with elastic members 25-26 (Figures 3-4) having an end eye 27-28 through which warp thread 8 and 7, respectively, is made to pass; these elastic members act therefore as heddles; they consist of V-bent steel wires as shown in Figures 3 and 4, are fastened in 29-30 to fixed parts of the loom and can therefore bend and extend under the action of the respective tie rods when they are alternately driven by the oscillating wings. In Figure 4, 25' and 26' indicate, in dashed lines, the same eye-bearing elastic elements 25-26 when they assume the most extended position; the distance or aperture between the lower position of element or member 25 (or 26) and the upper position 25' (or 26') constitutes the wave pitch necessary to allow the passage of shuttle 31.

In Figure 4, 32 indicates a generic weft thread carried by shuttles 31, while 33 and 34 indicate elastic members, angle-bent and fixed to the fixed portion of the loom, such elastic members being of the conventional type and having the function of providing the necessary length compensation of the continuously fed warp threads.

The loom includes furthermore an usual cylindrical read 35 and a disc-shaped platform 36 transversally keyed on the top of shaft 1, the prevailing function of which is that of controlling the shuttle motion by means of particular shuttle- pushers and shuttle-guiding devices which will be described in the following.

As already mentioned hereinbefore, to obtain a good conformation of the wave pitch destined to reverse at every passage of the shuttle, hollow shaft 9 carrying the bushes must rotate with a number of revolutions twice the one of loom shaft 1 for four-shuttle looms, three times that of shaft 1 for six-shuttle looms and, generally, in accordance with the formula indicated hereinbefore.

In practice, 8 pairs of oscillating wings distributed over the arc of 360° of a circumference are required to achieve an acceptable wave pitch.

To obtain a higher continuity in the sinusoidal motion of the heddles forming the so-called-wave shed, it is advisable to arrange a higher number of pairs of oscillating wings wherefore, in practice, though not strictly necessary, thanks to the capability of the shuttle to complete by itself the opening of the threads in virtue of a further specific arrangement concerning the read-shuttle coupling-such arrangement being illustrated hereinafter-more than four wings are utilized, so dividing the loom into a number of sectors multiples of 2, 4, 6 depending on whether the loom has 2, 4, 6 shuttles.

In the practical case of a loom having 4 shuttles, it is sufficient to use 8 or 12 wings indifferently.

Figure 5 illustrates, developed in plane, the conformation of the wave shed between two warp threads and in particularthe development of a quadrant (90°) of a loom, indicated by A, and the corresponding rotation of bushes 12-13 etc. over an arc of 180°, indicated with B.

The prefixed inclination angle of axis Z' of a bush around fixed axis Z, passing from the starting position to the one at 45°, 90° etc. involves oscillations of the wings such as to obtain a sufficient and almost regular opening of warp threads 8-7, which is suitable for the penetration by shuttle 31.

In Figure 5, the not dashed area between threads 7-8 represents the wave shed. Preferably, to improve the functionality of the loom, reed 35 is shaped so as to centrally contain a groove 37 (Figure 6) suited to act as a guide for the shuttles which, to this purpose, are equipped with a central sliding shoe 38 firmly inserted in said groove; the usual slipping supports of the bobbin on the upper and lower inner edges of the vertical-blade reed are so eliminated. It follows that in such embodiment the warp threads are not pressed between shuttle and reed edges, but are free to move forward. Furthermore, groups of supporting wheels 39-40 are associated with each shuttle so as to avoid the sliding friction against the reed and to further reduce the noise of the loom. Each group of wheels 39-40 actually consists of a tern of idle wheels 39_a‾39_b―39_c (Figure 7) and for each bobbin four groups of idle wheels are provided,-each of such groups comprising three wheels; each tern of wheels has centers of rotation slightly offset to one another and lying on a circumference coaxial with the reed circumference, as shown in Figure 7, wherefore during the sliding of the shuttle on blades 41 of reed 35, there is always a wheel which is surely supported on said blades, what ensures a continuous and regular sliding free from jerks.

In fact, in Figure 7, in position P of group of wheels 39 at least wheel 39a surely rests on a blade, in position P₁ two wheels, namely 39a and 39_o are stably supported, while in position P₂ at least wheel 39_c is stably supported.

The motion of the shuttles is obtained (Figure 4) with the shuttle pushing means rotating on cylindrical surfaces coaxial with the reed surface; these known shuttle pushers are equipped, according to the invention, with wheels 42 friction motor-driven against the base of reed 35 in consequence of the rotation of supporting plate 36; the rotation of wheels 42 is transmitted, through wheels 43_-44 and relevant belt 45, to shuttle-pushing wheel 46; such solution permits the passage of the warp threads, emerging from the bottom and directed upwards, through the contact area between the shuttle pusher and shuttle (Figure 4).

The loom illustrated hereinabove, fed according to any of the conventional methods, permits, also due to the particular shuttle-reed coupling, to design very high shuttles containing bobbins of great capacity and such as to ensure a high productivity of the loom and a very low noise degree.