SPIRAL ELEMENT FOR SUPPLYING TEXTILE FIBRE SLIVERS WITH COMPENSATION AND FALSE TWIST

Abstract: The invention relates to a movable sliver guide element (7) for the winding of cross-wound bobbins on the drawing frames (2), consisting of a spiral (10) with arc-shaped axis helical winding having a positive inner diameter, inside which said sliver (6) is made run and slide, so that it results guided and continuously twisted on itself, in order to be supplied with a high mutual cohesion between the fibres which compose it. In such a way, the movable spiral-shaped sliver guide (7) supplies the same sliver with a torsional strength suitable for elastically compensating for the periodic change of the distance between the stationary outlet point from the outlet calenders (3) of the drawing frame, and the collection point, which reciprocates along the bobbin (30) under way of formation.

Description: The present invention relates to a twisting and compensating device suitable for guiding a textile fibre sliver between the outlet calender of a drawing frame and a winding unit. In the following disclosure, and in the appended claims, the term "sliver" will be uniformly used in order to indifferently indicate both a roving of textile fibres, or a sliver of textile fibres, or, anyway, an aggregate of textile fibres. On a drawing frame on which the sliver is collected on bobbins of a traditional type, the bobbin is produced by winding the sliver around an idle roll, driven to revolve by one or more slotted rolls, by means of a false twisting device which gives the sliver roundness and mechanical strength, and maintains the individuality thereof during the subsequent unwinding process. It is known that the conveyance of the sliver, between the outlet calender of the drawing frame and the winding unit, must take place under a due collection tension, which is essential for a compact bobbin to form. Furthermore, the winding should be carried out with the fibres of the sliver being kept as condensed as possible, in order that the mutual cohesion between the fibres prevents false drawings from occuring over the length of sliver running from the drawing frame outlet to the surface of the bobbin under way of formation. Often, the sliver leaving the outlet calender is fragile owing to the fact that the textile fibres which constitute it are short, or are often connected with a low mutual cohesion degree. Furthermore, the sliver is continuously subject to a pendular change in distance between the stationary outlet point from the outlet calender of the drawing frame, to the movable sliver guide driven to reciprocate parallel to the axis of the bobbin under way of formation. Changes in the distances during the collection step must give the sliver such tension values, which will not cause modifications to occur in size and quality characteristics of the same sliver between the outlet point from the outlet calender, and the point wherein the winding operation is carried out. Relatively high changes in tension could even cause the sliver to break. One can easily understand how such a breakage would interrupt the production process, obliging the attending operator to take action. The labour cost for these emergency operations represents a considerable factor when the production costs are computed. In order to solve this winding problem, several solutions have been proposed in the past. US-A-3,670,978 proposes, e.g., to make the sliver run inside a ring constituting an intermediate guide, installed, in a movable way, between the point of outlet from the outlet calender of the drawing frame and the bobbin winding unit, in such a way that the total of the respective distances of said ring relatively to the outlet from the outlet calender and to the sliver guide remains always constant. On the same principle, moreover, several systems have already been proposed and implemented, which envisage, e.g., articulated toggle-levers, or the like, capable of realizing the desired kinematic system. However, these solutions suffer all from drawbacks, in that they require that relatively high masses be reciprocated, which cannot be applied to the present machines, operating at high speeds, not only due to the large energy amount to be supplied and to the fast wear occurring in the various parts, but also owing to the fact that vibrations, and consequent fatigue breakages, occur. EP-A-0 070 814 discloses a device for compensating the variable distance between the slider outlet point from the drawing frame and the movable point in which the winding operation takes place. In one embodiment of this known device an entry guide ring, a spiral element and a condenser sleeve are provided, wherein the centre of the helical windings of the spiral element, of the guide ring and of the inner surface of the condenser sleeve are disposed along an arc-shaped curve having its bending centre opposite to the bending centre of the winding of the sliver on the bobbin relatively to the trajectory along which the sliver is running. The entry guide ring consists or closed coils of the spiral element and is secured to the drawing frame at the exit of the outlet calender. The outlet end of the spiral element is secured to the inlet of a revolving condenser sleeve borne by the bobbin winding carriage. Thus, the sliver leaving the outlet calender of the drawing frame is guided along the whole length between the outlet calender and the condenser sleeve and is subjected to fast wear due to the frictional contact with the spiral element over a considerable part of its length. Furthermore, the known device not only is rather complicated from the constructive standpoint, but it also requires relatively high masses to be reciprocated with consequent large energy dissipation and generation of vibrations which give rise to further damages of the fibre sliver. The purpose of the present invention is to improve this last mentioned device in order to supply the sliver leaving the outlet calender of the drawing frame with an effective false twist, compacting the fibres with one another and making the sliver strong enough for the cross-winding operation. Said purpose is achieved according to the present invention with the features defined in the characterising portion of claim 1. The spiral element of the device can be constituted by a wire or a tube made from spring-steel or another wear-resistant material, helically wound with a pitch and with a number of turns which depend on the type and weight of the textile fibre sliver to be processe . Inasmuch as the whole device is integrally connected to the reciprocating bobbin winding carriage and is not secured to the exit of the outlet calender of the drawing frame, whereby the sliver is guided only over part of its whole length before entering the condenser sleeve, the device has the very small inertia as necessary in order not to substantially apply a burden to the bobbin winding carriage, together with which the whole device is movable during its reciprocating motion. The spiral element gives twists to the sliver, supplying it with such a bond strength and such a compactness between the fibres, as to render it totally elastic and capable of supporting the necessary tension to be applied for performing the cross-winding operation. More specifically, the spiral element performs the task of guiding the sliver to the surface of the bobbin under way of formation, with simultaneously supplying the same sliver with a twist in a predetermined direction running towards the outlet calender. Such a twist, by running along the entire length of the sliver, arrives up to the outlet point from the outlet calender, and is more concentrated along those sliver portions wherein the cross-section surface area is smaller, thus compensating for their lower strength relatively to the other sliver portions, which have a larger cross-section surface-area. One can easily understand that all the above gives the sliver a uniform strength along its whole length, eliminating those portions characterized by a low twist strength which may easily generate breakages, and therefore cause interruptions of the productive process, with such consequences as above partially mentioned. Thus, the twist given by means of the spiral element to the sliver, when this latter leaves the outlet calender, keeps advantageously mutually bound the fibres which compose the same sliver, making it possible said sliver to be put under tension, in order to elastically extend it, realizing a perfect compensation for the change in distance, with no risk of formation of false drawings. Thanks to the simple structure and to the low weight of the spiral element, the bobbin winding speed can be substantially increased on the machine, and the cost of the same machine is decreased to a considerable extent. The helical windings of the spiral element, by being prearranged along an arc-shaped curve, whose bending centre is opposite to the bending centre of the winding of the sliver on the bobbin relatively to the trajectory along which the sliver under way of collection runs, contribute to considerably improve the twisting of the sliver and to perfectly round it. In fact after several experimental investigations, it was possible to observe that the arc-shaped axis of the spiral element leads to that constancy of the circular shape of the cross-section of the sliver which is being continuously wound, which makes it possible the presence to be eliminated of the so-said "mariages", i.e., the binding of fibres of adjacent sliver turns, which generate faults during the subsequent step of the production process, operating on bobbin unwinding. According to a form of practical embodiment, the inner diameter of the helical windings of the spiral element is positive and, substantially constant. According to a another form of practical embodiment, the inner surface of the condenser sleeve has a spherical outline converging in the direction of collection of the sliver, in order to gradually compact the sliver before it is collected on the surface of the bobbin under way of formation. According to a further form of practical embodiment, the inner surface of the guide ring has a substantially spherical outline. According to a still another form of practical embodiment, the spiral element is provided with two ends, with one of said ends being fastened to anchoring elements connected to the reciprocating bobbin winding carriage, and the other end being fastened to the entry guide ring. In the following a preferred form of practical embodiment of the device according to the present invention is described for solely exemplifying and non-limitative purposes, with the aid of the hereto attached drawing tables, wherein: Figure 1 shows a schematic side view of the device in upstream cooperation with the outlet calender through which the sliver leaves the drawing frame, and in downstream cooperation with the cross-winding unit for the formation of the cross-wound bobbin on which the sliver is collected. Figure 2 shows a schematic view of the arc-shaped spiral element together with the cross sections of the entry guide ring, and of the exit condenser sleeve. In the figures, equal parts, or parts performing equal or equivalent functions are indicated by same reference numerals: In the figures: 2 is a schematic outline of the drawing frame, or of a derived machine; 3 is the outlet calender, which acts as the means for feeding the sliver leaving the drawing frame 2; 4 is the pressure roll of the outlet calender, which, together with the roll 5, continuously extract from the drawing area the fibre sliver 6; 6 is the sliver of textile fibres substantially constituted by an aggregate of a more or less large number of textile fibres of various length; 8 is a entry guide ring with a side slot. This latter, not depicted in the figures, as being per se known, is advantageously provided in order to make it possible the sliver 6 to be entered inside the ring 8. Said ring is given an inner ring surface with a substantially spherical outline in order to correctly guide the sliver into the interior of the spiral element 10; 10 is a spiral element with a plurality of helical windings not mutually coaxial, but predisposed along an arc-shaped curve 16 whose bending centre is opposite to the bending centre of the winding of the sliver 6 on the bobbin 30 relatively to the trajectory along which the same sliver 6 runs; 7 is the initial portion of the spiral element 10 wherein the fibres of the entering sliver 6 exert a higher pressure, due to the bent arrangement of the helical windings according to the axis 16, onto the intrados 11 of the inner surface of said spiral element 10, which is characterized by an inner positive diameter; 9 is the end portion of the spiral element 10, wherein the fibres of the exiting sliver 6 exert a higher pressure, due to the circumferential deviation of the sliver 6 under way of collection on the bobbin 30, against the extrados 15 of the inner surface of said spiral element 10; 12 is the condenser sleeve whose inner surface has a spherical outline converging in the direction of collection of the sliver 6 on the bobbin 30; 14 and 18 are connection brackets for creating an integral connection between the condenser sleeve 12 and the reciprocating bobbin winding carriage 20 guided to move parallel to the axis of the bobbin 30 under way of formation; 24 is a sleeve sliding along a cylindrical guide bar 22 positioned parallel to the axis 34 of the roll 32 which drives the bobbin 30 under way of formation; 26 is the flat structural shape which supports the carriage 20 provided with reciprocating motion with a transversal stroke substantially equal to the axial length of the desired bobbin 30. The sliver, or roving, or aggregate of fibres 6 leaving the outlet calender 3 is entered into the guide ring 8 through the side slot, not shown in the figures, as being per se known,and is conveyed,through the spiral element 10 and the condenser sleeve 12 in order to be collected on the periphery of the bobbin 30 under way of formation revolving on the winding spindle 28. In the present disclosure, a preferred form of practical embodiment of the present invention has been disclosed, but other different forms of practical embodiment are possible as well; the shape, the ratios and the size of the parts may be changed; the wire which constitutes the spiral element 10 may be of a different suitable material; the anchoring elements 14 and 18 may be given a different shape, or may be mounted in a different way, without thereby departing from the scope of the solution as proposed by the present invention, as claimed in the hereto appended claims.

Claims: Twisting and compensating device guiding a textile fibre sliver (6) between the outlet calender (3) of a drawing frame (2) and a winding unit having a bobbin winding carriage (20) reciprocating parallel to the axis of the bobbin (30) being formed, comprising an entry guide ring (8), a spiral element (10) and a condenser sleeve (12), the centres of the helical windings of said spiral element (10), the centre of said guide ring (8) and the centre of the inner surface of said condenser sleeve (12) being predisposed along an arc-shaped curve (16) having its bending centre opposite to the bending centre of the winding of the sliver (6) on the bobbin (30) relatively to the trajectory along which the sliver (6) is running, characterized in that the whole device (8,10, 12) is integrally connected only to the reciprocating bobbin winding carriage (20) so as to be movable together with said carriage. Device according to claim 1, characterized in that said spiral element (10) has two ends, with one of said ends being fastened to said guide ring (8) and the other end being fastened to anchoring elements (14,18) connected to said bobbin winding carriage (20), said anchoring elements (14,18) also bearing said condenser sleeve (12). Device according to the preceding claims, characterized in that the inner diameter of the helical windings of the spiral element (10) is positive and substantially constant. Device according to any of the preceding claims, characterized in that the inner surface of said guide ring (8) has a substantially spherical outline. Device according to any of the preceding claims, characterized in that the inner surface of said condenser sleeve (12) has a spherical outline converging in the collection direction of the sliver (6).

Inventors: MINGUZZI, ERALDO, SARTONI, SANDRO
Applicants: SAVIO S.P.A.
Application year: 1988
Main classification: B65H57
IPC codes: B65H57, B65H59, B65H54