UNWINDER ARM ROTATING ABOUT A PIVOT SUSPENDED ABOVE A TWO-FOR-ONE TWISTING SPINDLE FOR UNWINDING SUPERPOSED BOBBINS

Abstract: This invention relates to an unwinder device for guiding the yarn and comprising a arm (1) rotated by the tension in the yarn (7) unwinding from the feed bobbin (14), this latter located in the feed box (9). More specifically, the invention relates to an unwinder element suitable for direct twisting on a two-for-one twisting spindle, said unwinder element rotating about a pivot (2) located in the space defined between the upper end of the spindle head (30) and the upper yarn guide eye (18), which represents the vertex of the balloon envelope formed by the twisted yarn as it rotates freely about the bobbin carrying chest. Said unwinder element is supported by a frame (5) resting and hinged on the box (9) containing the two superposed bobbins (14, 16) and advantageously allows any underlying unwinder arm (22) fixed to the upper part of the hollow spindle shank to also rotate.

Description: The invention relates to a two-for-one twisting spindle arrangement for twisting together a number of yarns to form a twisted yarn. Said yarns can be of any composition or structure, the term "yarn" being used interchangeably in the description and claims given hereinafter to indicate both the yarn to be twisted and the twisted product itself, and to include all natural or artificial filaments, filament assemblies or fibres. The term "twist together" is used here in the widest sense of combining two or more yarns, and in this sense can include twisting together previously twisted yarns. Although the invention is particularly useful for twisting together two yarns it can be used for combining three or more yarns, the limit being dictated only by practical considerations. It is well known that in a two-for-one twisting spindle the yarns to be twisted together are unwound upwards from at least two bobbins located on a fixed mandrel. This known unwinding operation has the drawback that the yarns may interfere with each other and become tangled before entering the central hole in the spindle, thus forming loops, rings, spiral corkscrew-shaped portions and shapes of this kind. It is also well known that the unwinding yarns in a two-for-one twister, especially of high-speed operation, are exposed to tension variation which is sometimes excessive. If several yarns are concerned, whether yarns spun from flock or synthetic filament yarns, this excessive tensioning is undesirable because the yarns undergo severe stressing and friction contact whenever they tangle during their continuous unwinding from the feed bobbins, and they consequently become excessively stretched, damaged or broken. This generates interruptions in the production process and therefore impairs the economics and productivity of plants of this kind. Two-for-one twisting spindles of this construction have the further drawback that during unwinding the yarn is caused to rest and slide on the outer peripheral surface of the feed bobbins, thus damaging the yarn by abrasion and reducing its strength. There is therefore the danger that the aforesaid interfering of the yarns, which as they unwind rotate in orbits about the bobbins, and the aforesaid sliding along the outer peripheral surfaces of the bobbins themselves, lead to the formation of flying dust and fibrils, which after a certain time become twisted together with the yarns and can result in twisting defects. Again, this repeated yarn intersection and the said frequent sliding contact along the outer surfaces of the feed bobbins can result in a greater energy requirement per spindle and therefore an increased cost of the twisted yarn product. Many attempts have been made to ensure that the yarns unwinding from the bobbins mounted on the bobbin carrier coaxial with the hollow spindle do not undergo mutual interference during their orbital unwinding rotation before penetrating into the open end of the spindle. Typical examples of these attempts of the known art are unwinder arms positioned at the top of the spindle (FR-A-1328 653) or also in the middle between the superposed feed bobbins (DE-A-1159 826 and DE-A-1905 049), or alternatively at the bottom below the unwinding bobbins (DE-A-1159 827). Said arms are entrained by the yarns and rotate about the spindle shank by being centered thereon, and for a considerable time have been used as an unwinding and guiding aid for the yarns to be twisted. In addition, discs or plates of various shapes are known which, centered and positioned horizontally about the spindle at its top or in the middle between the superposed bobbins, guide the yarns to be twisted by separating them from each other along the path between the unwinding zone and the top zone in which they enter the spindle. The use of such yarn guides does not represent a satisfactory solution to the problem in the production of twisted yarns in two-for-one twisting spindles. In this respect, these known-art applications frequently result in non-uniform twisting because of the variation in yarn tensioning conditions deriving from the different and sometimes intricate guiding of the individual unwinding yarns. This effect is undesirable because it ruins the appearance of the twisted yarn and also results in a reduction in its resistance to tear because the individual yarns when subjected to a pulling force undergo non-uniform loading. In the case of very thin yarns undergoing particularly rapid unwinding, this can result in breakage. In addition, the aforesaid known devices are rather complicated and costly in their construction and application and are also rather difficult and complicated to handle when the bobbins have to be replaced. DE-A-1 159 826 shows a thread guide arrangement for two-for-one twisting spindles of the kind referred to in the preamble of claim 1. This known device has most of the above mentioned drawbacks and especially does not allow a uniform twisting of the yarns owing to the substantially different tensioning conditions of the yarns caused by different yarn paths and engaging conditions with the thread guides. It is furthermore complicated to replace the empty bobbins because this requires substantial removal of parts from inside the cylindrical box housing the superposed bobbins, and then remounting these parts still within the bobbin box. The object of the present invention is to obviate the aforesaid drawbacks. This is achieved by a spindle arrangement having the features claimed in claim 1. The spindle arrangement of the present invention has the following advantages: it eliminates the formation of loops, rings and spiral corkscrew-shaped portions while maintaining the tension in the yarns unwinding from the feed bobbins substantially constant; it reduces breakages to a level substantially lower than any other known arrangement, by making the yarns unwind in a more suitable manner; it enables any yarn structure, including cotton, to be twisted on a two-for-one twisting spindle operating by direct twisting, practically without regard to its composition or structure; it allows yarns unwinding from bobbins of considerable axial length and taking any unwinding path to be guided separately for twisting purposes; the limit depends only on the dimensional ability of the twister to hold the bobbins; it enables the twister to use conical feed bobbins of any angle up to 5° 57′ and also allows the twister to use two superposed bobbins with yarns of different fibre and of different count, because the braking of the upper unwinder arm of the present invention, done by systems known in the art, is independent of the braking of any other unwinder elements which are present. A further advantage of the arrangement of the present invention is that the yarn of the lower bobbin is enabled to run at the correct distance from the other feed yarns, so that there is no possibility of the yarn of the lower bobbin to intersect the other yarns, with the result that it does not rub against them and is therefore not subject to wear. This latter advantage enables a twisted yarn to be obtained which is of improved quality at lower operating cost. This improved quality derives from the lack of sliding contact between the individual yarns with consequently no generation of dust or flying fibrils, as the individual yarns take different paths during the entire unwinding stage. In this respect, the guide eye at the end of the unwinder arm supported above the spindle guides the yarn unwinding from the lower bobbin in an upper rotary orbit surrounding the rotary orbits of the other unwinding yarn or yarns. In practice it is a substantial advantage that said unwinder arm together with its support can be mounted from above on the box containing the two or more superposed bobbins and can thus be easily mounted and removed without effort. Advantageous mounting arrangements for the unwinder arm are claimed in claims 2 and 3. Thus tools are not required either for mounting the unwinder arm of the present invention on a two-for-one twisting spindle, or for removing it therefrom. Thus no constructional modification is necessary in order to be able to mount said unwinder arm on an existing two-for-one twisting spindle. The invention will be more apparent from the detailed description of embodiments thereof given hereafter with reference to the two accompanying drawings, together with further clarification of its characteristics, it being however understood that the invention is not limited to these embodiments alone. In the drawings: Figure 1 is a diagrammatic partial axial section through a two-for-one twisting spindle arrangement according to a first embodiment of the invention. Figure 2 is a diagrammatic partial axial section through a two-for-one twisting spindle arrangement according to another embodiment of the invention, showing by dashed lines the position of the upper unwinder arm when reclined so that it forms an angle to the spindle axis sufficient to give access to the superimposed feed bobbins to enable them to be replaced. In the figures, corresponding parts carry identical reference numerals for simplicity. Furthermore, in the figures those parts of known two-for-one twisting spindles not directly concerned with the invention are omitted for clarity. The accompanying drawings show an unwinder arm 1 idly rotatable about a pivot 2 by the tension of a yarn 7, this latter being unwound from a lower bobbin 14. The arm 1 can have any shape provided that it is thin. It is however essential that the material is a light metal or non-metal, so that its final weight is small in order to give it the low inertia necessary for its rotary entrainment. The pivot 2 is located vertically above the hollow spindle. The unwinder arm 1 is carried by a rotating ring 3 with which the unwinder arm 1 is made rigid. A fixed hub 4 integral with the pivot 2 is used for connection of the pivot 2 to a support frame formed by one or more bars 5 (Fig.1) or 15 (Fig.2) which are connected at the bottom to a tubular housing member 8 in the form of a hollow cylindrical band. A guide ring or eye 6 for the yarn 7 is provided at the free end of the unwinder arm 1. Its purpose is to ensure that the yarn 7 slides with perfect ease, and it must be constructed of a wear-resistant material. The member 8 is elastically fitted onto the upper edge of a tubular bobbin carrying box 9 which contains the superposed feed bobbins 14 and 16 and is prevented from rotating by stop magnets or the like (not shown). A thin intermediate disc 10 aids the guiding of the yarn 7 unwinding from the lower bobbin 14. The yarn 20 of the upper bobbin 16 is unwound by an unwinder arm 22 pivoted to rotate freely about the axis of the spindle between a hollow shank portion 32 and a ring 26, the arm 22 being entrained by the tension of the yarn 20. The ring 26 is however not essential. A guide ring or eye 24 for the yarn 20 is provided at the free end of the unwinder arm 22 and is necessarily constructed of a material which resists the continuous sliding of the yarn 20. As shown in the drawings, the guide eye 6 is located in a radially outer position with respect to the guide eye 24. The yarns 7 and 20 enter a hollow head 30 of the hollow spindle to form a twisted yarn 12 emerging radially at the bottom of the spindle through a duct 23 provided in a yarn collecting disc 27. The twisted yarn 12 is then led upwards, forming a yarn balloon, to a yarn guide eye 18 which defines the vertex of the balloon. A tubular housing 28 contains the balloon formed by the twisting yarn 12. The twisting yarn 12 then continues its upward movement in the direction of the arrow 21 to feed a winding unit (not shown). The head 30 of the twisting spindle is arranged coaxially on the hollow shank portion 32 of the spindle. The axis of the pivot 2 about which the unwinder arm 1 rotates is substantially coincident with the axis 34 of the spindle. The support frame 5 of the embodiment of Fig.1 is rigid with the member 8, whereas the support frame 15 of the embodiment of Fig.2 is pivoted to the member 8 by a hinge 11 which enables the unit comprising the support frame 15 and the unwinder arm 1 to be reclined to facilitate insertion of new superposed feed bobbins. In Fig.2 the position assumed by the frame 15 after being rotated about the pin of the hinge 11 is indicated at 15a, whereas 1a, 2a and 3a are the positions assumed respectively by the elements 1, 2, 3 after the frame 15 has been reclined, ie after it has been rotated about the pin of the hinge 11. The operation of the twisting spindle arrangement according to the present invention will now be described with reference to Figure 1, Figure 2 showing a constructional configuration for which the operation is then easily derivable. The feed bobbins 14 and 16 are superposed within the box 9 and are kept centered coaxially about the spindle. The yarn 20 unwinding from the upper bobbin 16 is led upwards through the guide eye 24 of the unwinder arm 22 and is then inserted, together with the yarn 7 unwinding from the lower bobbin 14, through the hole in the head 30 of the hollow spindle. The yarns 7 and 20 are then withdrawn together radially from the yarn collecting disc 27 through the duct 23 and are both led upwards within the annular space between the balloon container 28 and box 9. During this initial insertion, the yarn 7 is passed directly from the bobbin 14 to the inlet hole in the head 30. Having completed this stage of the insertion the unwinder arm 1 and its upper support frame 5 are mounted by elastically fitting this latter with the tubular housing member 8 onto the upper edge of the box 9. With the unwinder arm 1 so positioned, the yarn 7 is inserted into the guide eye 6 and the passage of the twisted yarn 12 formed from the yarns 7 and 20 twisted together is completed by inserting the yarn 12 through the yarn guide eye 18 which defines the vertex of the balloon envelope of the twisted yarn 12. The twisted yarn 12 then continues its path through drawing rollers and yarn guides to be wound onto a bobbin in a known manner. The twisting spindle arrangement is now set in motion and the two yarns 7 and 20 are drawn through the central hole in the head 30 and unwind from the feed bobbins 14 and 16 totally independently of each other, ie without ever coming into mutual contact, as the action of the unwinder arm 1 and its guide eye 6 obliges them to describe surfaces of revolution which are different from each other and which never intersect. It is apparent that owing to the support of the unwinder arm 1 above the spindle head 30 and the extension of the arm 1 above and externally to the path of the yarn 20, the two yarns 7 and 20 do not come into contact before entering the funnel-shaped entry hole in the head 30. The arrangement according to the invention, which is both simple and reliable in operation, can be applied with particular advantage to all typical twisted fibre assemblies such as worsted yarns, carded wool yarns, cotton yarns, cellulose wool and mixed yarns. The arrangement of the invention is also suitable for the direct twisting of more than two superposed bobbins. Preferred embodiments have been described herein. It is however apparent that modifications to aid unwinding can be made thereto which fall within the scope of the present invention. Thus the positions of the guide eyes 24 and 6 can be different from those proposed, for example both can be disposed within the annular space between the bobbin 16 and box 9, or can be disposed at different heights, for example the eye 6 in a higher position than the eye 24 or vice versa. The frame 5 can be modified in terms of shape and size and can consist of support bars of any number and shape, which can for example be in the form of lateral surface portions pertaining to solids of revolution. The rotary ring 3 can be replaced by any device which allows rotation about an axis coincident with the axis of the spindle and is arranged above the spindle.

Claims: A two-for-one twisting spindle arrangement for twisting yarns (7,20) fed by two or more superposed bobbins (14,16) arranged coaxially about a hollow spindle, wherein the yarns (7,20) are guided between the respective bobbins (14,16) and a hollow spindle head (30) by respective guide eyes (6,24) provided on respective unwinder arms (1,22) arranged rotatably about the axis (34) of the spindle, the guide eye (6) for the yarn (7) of the lower bobbin (14) being located in a radially outer position with respect to the guide eye (24) for the yarn (20) of the upper bobbin (16), characterised in that the unwinder arm (1) provided with the radially outer guide eye (6) is supported above the spindle head (30) and extends above and externally to the path of the other yarn or yarns (20). A spindle arrangement according to claim 1, characterised in that the unwinder arm (1) provided with the radially outer guide eye (6) is rotatably suspended on at least one bar (5) fixed to a tubular housing member (8) removably fastenable onto a tubular box (9) surrounding the superposed bobbins (14,16). A spindle arrangement according to claim 1, characterised in that the unwinder arm (1) provided with the radially outer guide eye (6) is rotatably suspended on a bar (15) hinged onto a tubular housing member (8) removably fastenable onto a tubular box (9) surrounding the superposed bobbins (14,16).

Inventors: COLLI, LUIGI
Applicants: SAVIO S.P.A.
Application year: 1988
Main classification: D01H7
IPC codes: D01H7