TITLE

Device for cutting yarns and light fabrics in textile machines .

DESCRIPTION The present invention relates to a device for cutting yarns and light fabrics in textile machines, such as weaving and hosiery machines.

Shears consisting of a fixed cutting plate or blade and a mobile cutting plate or blade are commonly used to cut yarns in textile machines such as looms and the like. The mobile plate is applied onto a shaft which is oscillated around its longitudinal axis by means of a cam drive or a beating device. Use of a cam, as well as use of a beating device, requires a mechanical force applied to the mobile blade and further requires a negative phase which is necessary to bring the mobile blade back into its opening position by means of a return spring, the latter also providing adhesive conditions between the mechanical parts of the shear and ensuring the necessary adhesion between the mobile blade and the fixed blade. This results in a mechanism requiring a suitable structure capable of bearing the stress caused by the oscillating motion of the blade. Nevertheless, wear effects occur, the more economical and of poorer quality the materials used are, the quicker and more evident these effects are.

A further remarkable inconvenience is caused by the fact that these well-known mechanical devices are to be positioned at predetermined points of the machine and, moreover, in case of a block of a mobile blade, they are exposed to serious damages, as the mechanical thrust necessary to operate them, that is to say necessary to obtain the closing or cutting positioning of the mobile blade, is produced at any rate, whatever

resistance they may meet. These devices are to be adequately protected in order to avoid injuries to the operators who might accidentally put their fingers or hands between the blades. Therefore, if the shears are positioned at a certain point of the machine which is particularly exposed to such risks, it is necessary to provide suitable and relatively expensive safety protections. In recent times, it has been proposed to use cutting devices driven by a motor and comprising a cam controlling the oscillation of a lever connected to the mobile blade. These devices allow the disengagement of the shears from the mechanical organs of the textile machine, but they are in the same way dangerous in case high-power motors are employed and, if low-power motors are used, they may be subject to irreversible block, unless the operator intervenes, thus adversely affecting the manufacturing process. Moreover, springs and similar parts are provided to ensure adhesion of the mobile blade to the fixed blade. Even in this case, in order to realize a good quality product, it is necessary to bear relatively high costs. The main purpose of the present invention is to eliminate or at least to remarkably reduce the above mentioned inconveniences.

These results have been achieved, according to the present invention, by providing a device having the features described in claim 1. Further features of the present invention are the subject of the dependant claims.

The structure of the present device allows the reduction of the space it occupies to the minimum as well as the reduction of the number of its components; it is possible to avoid damages to the system in case

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of a very improbable block of the blade, to reduce power consumption, to reduce noise, to avoid dissipations due to the elastic connections, to adjust the operating parameters in the desired way (for example the frequency and oscillation amplitude of the mobile plate) by simply acting on the control electronics without modifying the arrangement, the shape or the geometry of the components. Moreover, the present device is lighter, relatively cheap, rugged, reliable and extremely safe. This leads to advantages in terms of operating management of the device itself, as it does not require any routine maintenance or lubrication of its parts. These and other advantages and characteristics of the present invention will be best understood by anyone skilled in the art from a reading of the following description in conjunction with the attached drawings given as a practical exemplification of the invention, but not to be considered in a limitative sense, wherein: ,

- Fig. 1 shows a schematic transparency perspective view of a shear according to the present invention;

- Fig. 2 shows a perspective exploded view of the shear shown in Fig.l; - Fig. 3 shows a perspective exploded view of the shear of Fig. 1 with some parts removed to better show other parts;

- Fig. 4 shows a schematic bottom plan view of the shear of Fig.1; - Fig. 5 shows a section view along the line A-A of Fig. 4;

- Fig. 6 shows a schematic perspective view of the inductor set;

- Fig. 7 and 8 show two views of the inductor set of Fig. 6 on two different orthogonal planes;

- Fig. 9 is a section view along the line B-B of Fig. 8;

- Fig. 10 shows a schematic transparency perspective view of a shear according to a further embodiment of the present invention.

Reduced to its essential structure and with reference to the figures of the enclosed drawings, a shear according to the present invention comprises a fork- shaped support structure (1) with two parallel arms (10,11) joined together on the rear side of the support and provided with coaxial, transverse passing holes (12,13) at the corresponding free ends, that is to say on the front side of the support. In said holes (12,13) two corresponding bushings (14,15) are provided, through which a shaft (2) is positioned, said shaft being orthogonal to the lateral arms (10,11) of support (1).

Said shaft (2) features a portion (20) emerging laterally from one of said arms of the support (1) . With reference to the example shown in the enclosed drawings, said shaft (2) is positioned so that a portion (20) thereof emerges laterally beyond the left arm (11) . A mobile plate blade (30) of the very shear

(3) is fixed on said portion (20) of shaft (2) . On this purpose, said mobile plate (30) features a lower extension (31) with a hole through which said emerging part (20) of shaft (2) passes. The fixing of said mobile plate (30) to said shaft portion (20) is carried out by means of a nut (23) tightened on the threaded end of the shaft. Therefore, any oscillation to which the shaft (2) is subject, that is to say each rotation about the longitudinal axis of the shaft, is correspondingly transmitted to the mobile plate (30) of shear (3) . The shear (3) further comprises a fixed cutting plate

(32) which is mounted onto the front end of the same arm (11) from which emerges the portion of the shaft (2) supporting the mobile plate (30) .

A rod (4) is mounted on the central portion of shaft (2), that is to say on the portion of shaft (2) resulting between the side arms (10,11) of support (1), said rod being parallel to said arms, that is to say orthogonal to shaft (2) . The front end of connecting rod (4) is clamp-shaped and is tightened on shaft (2) by screw tightening means (40). The rod (4) extends backwards between the two arms (10,11) of support (1) and its rear end faces the rear end of the latter. In practice, the rod (4) is an extension of shaft (2) and is operated by an electromagnetic control device, further described below, which determines its oscillation with predetermined oscillation amplitude and frequency about the longitudinal axis of shaft (2) . According to the embodiment shown in the enclosed drawings, said electromagnetic control device comprises a plurality of elements positioned inside the two side arms (10,11) of support (1). More in detail, one arm (10) of support (1) is associated with an inductor (5) comprising two superimposed poles (50) contained in a resin shell (51) (of the type commonly used to encapsulate electronic components) and supported by a plate (52) which is fixed on the external side of the arm (10) by screw means (53) . Said arm (10) features a transverse opening (100) which houses said shell (51) with the two poles (50) of the inductor contained in it. Said poles are connected to a power supply by means of a cable (55) which can be connected to a connector (56) presented by plate (52) on its external side. Each of

said poles (50) comprises a tubular core (57) onto which a corresponding winding is mounted. The axes of the cores and those of windings (58) are orthogonal to plate (52) and to arm (10), that is to say they are orthogonal to the direction in which rod (4) mainly develops. The shank of a screw (59) passes inside each core (57) . The head of screw (59) is opposite to base plate (52) whereas the shank emerges from the external side of said base plate. Moreover, the head of screw (59) is tightened on a plate (590) which constitutes the end of core (57) turned towards the inside of support (1) . On the opposite side, the tightening of whole pole unit (50) and its fixing on base plate (52) by means of a corresponding nut (591) take place. Said pole units (50) are mounted as to provide an air gap of a predetermined value between the respective plates (590) . The rear end of the rod (4) houses a permanent neodymium magnet (45) , contained in a corresponding housing provided by the same rod; said permanent magnet is held close to the side of connecting rod (4) turned towards inductor (5) by means of a resin block (46), for example an epoxy resin block.

The arm (11) of the support (1) onto whose front part the cutting plate (32) is fixed, houses, in correspondence of the rear side of the rod (4), a permanent neodymium magnet (47), whose polarity is opposed to the previously cited magnet (45) , which is held in position by means of a resin block (48), for example an epoxy resin block. On its rear side, the support (1) features a clearance hole (12) so as to allow its mounting on a fixed part of a textile machine.

The operation of the above described device is as follows. By supplying the inductor (5) , that is to say its two

poles (50) , with direct current having a polarity inversion characterized by a predetermined inversion frequency, a magnetic field with a corresponding periodical polarity inversion is generated. By hooking magnet (45) housed in the tail of the rod (4), the thus generated magnetic field determines an alternate motion of the same rod which, being hinged to the two arms (10,11) of support (1) by means of shaft (2), determines a corresponding periodical oscillation of the latter about its longitudinal axis. This causes a corresponding oscillation of mobile blade (30) , that is to say the periodical opening and closing of shears (3) which allow the cutting of the yarn (not shown in the drawings) to be cut. Magnet (47), which is positioned in the arm (11) and whose polarity, as mentioned above, is opposite to magnet (45) contained in the rod (4), thanks to the attraction exerted on the magnet (45), controls the rotation about the axis of shaft (2) by limiting it so as to avoid using shoulders, springs or other mechanical means acting as stroke limit switches. In other words, magnet (47) exerts a limiting function on the alternate motion imposed upon magnet (45) by the two poles (50) of inductor (5) . Moreover, the effect of magnet (47) on magnet (45) increases, as the action exerted by inductor (5) on it decreases. In fact, in correspondence of each supplying wave (which preferably is a square wave) , the intensity of the action of inductor (5) on magnet (45) decreases as magnet (45) rotates about the longitudinal axis of shaft (2) because the part of magnet (45) progressively exposed to the action of the inductor decreases, whereas the action exerted by magnet (47) on magnet (45) is substantially constant. By adjusting the position of the rod (4) on shaft (2), that is to

say the distance marked with reference "d" in Fig. 5, it is possible to adjust the cutting pressure of shear (3) as, in this way, the force exerted by magnet (47), which tends to attract rod (4), and consequently mobile blade (30), towards arm (11) of support (1) and towards fixed blade (32) of the very shear (3) , is correspondingly adjusted.

The drawing in Fig. 10 shows a device according to the invention, in which the shear is mounted contrariwise in comparison with the case described above, that is to say with its blades (30) and (32) turned towards the rear side of support (1) . This arrangement involves that the whole device will have less total length. The structure and the operation of the device of Fig.l are identical to those shown in Figs 1-9.

By way of example, the device can be built with cutting plates (30, 32) in self-regenerating ceramic with an adjustable cutting angle, providing a cutting opening equal to 8mm, an oscillation amplitude of mobile plate (30) which can vary up to 10 mm and 20 oscillations per second with maximum amplitude. Tests carried out on an experimental device have detected a cutting force of about 1 Kg which is electronically adjustable by regulating the power transmitted by the power supply on inductor (5) even if, for most yarns used in the textile industry, the cutting force can be maintained at a remarkably lower value. This results therefore in further advantages in terms of operating safety. Thanks to the tests mentioned above it has been possible to verify an electric power absorption inferior to 10 W at the maximum value of the cutting force, as well as the fact that possible increases in temperature are easily compensable by means of a light tangential ventilation. The prototype used for the experimental tests has been fed with a continuous 12V

voltage with a polarity inversion having a frequency of 20 cycles per second. The rod (4), for example, can be built in aluminium.

The whole device looks compact and light and it requires extremely simple anchorages to the textile machine .

The oscillation amplitude permits mobile plate (30) to travel across the entire edge of fixed plate (32) so as to allow a long duration of the very shear and a basically constant self-sharpening.

It must be further pointed out that it is not necessary to carry out any mechanical maintenance or any lubrication of the mechanical parts. The above description gives evidence that the adhesion of the mobile blade to the fixed blade is guaranteed and controlled by the interaction of magnets (45) and (47) which attract each other with a force which is inversely proportional to their distance. Moreover, since magnet (45) features a pole which faces the elements (590) of inductor (5) , in addition to the oscillation due to the electronically obtained cyclical polarity inversion, an attractive force of the magnet (45) towards inductor (5) is produced. As magnet (45) is connected to shaft (2) by means of connecting rod (4) in which it is housed, said force pushes the mobile blade towards the fixed blade of shear (3) with an intensity which depends on the position of connecting rod (4) in the space between the two side arms of support (1) . The oscillation generated by inductor (5) is controlled and contained in a magnetic holding space which allows the mobile blade to carry out an oscillation with a regular amplitude sufficient to cover the whole edge of the fixed blade and to avoid anomalous wear. Moreover, it has been found that

whenever the mobile blade of shear (3) meets a certain degree of resistance ( for example in case the operator inadvertently puts a finger into the shear between the two blades) the angular amplitude of the oscillation decreases contrary to mechanical devices characterised by transmission rigidness, so as to correspondingly reduce or even to eliminate the risk of injuries for the operators' hands.

In practice, the execution details may equally vary as regards the shape, the size, the arrangement of the elements, the kind of material described above, but they are in accordance with the idea of the solution adopted and within the limits of the protection offered by the present patent.